Under the Partnership Agreement, the Issuer has agreed to register for resale under the Securities Act and applicable state securities laws any Common Units or other partnership securities proposed to be sold by GP or any of its affiliates or their assignees if an exemption from the registration requirements is not otherwise available. These registration rights continue for two years following any withdrawal or removal of GP as the Partnership’s general partner.

Further, the Partnership may from time to time increase the amount of its quarterly distribution to unitholders at the discretion of the board of directors of GP. The information provided under the caption “Partnership Agreement-Cash Distributions” under Item 6 below is hereby incorporated by reference herein.

As of the date of this Schedule 13D, none of the Reporting Persons, and to the Reporting Persons’ knowledge, none of the Listed Persons has any plans or proposals which relate to or would result in any of the following actions, except as disclosed herein and except that (i) the Reporting Persons or their affiliates or the Listed Persons may, from time to time or at any time, subject to market and general economic conditions and other factors, purchase additional Common Units in the open market, in privately negotiated transactions or otherwise, or sell at any time all or a portion of the Common Units now owned or hereafter acquired by them to one or more purchasers and (ii) members of the board of directors of GP may choose not to stand for re-election at the end of their respective terms:

·      the acquisition by any person of additional securities of the Partnership, or the disposition of securities of the Partnership;

·      an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Partnership or any of its subsidiaries;

·      a sale or transfer of a material amount of assets of the Partnership or any of its subsidiaries;

·      any change in the present board of directors or management of the Partnership, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board;

·      any material change in the present capitalization or dividend policy of the Partnership;

·      any other material change in the Partnership’s business or corporate structure including but not limited to, if the Partnership is a registered closed-end investment company, any plans or proposals to make any changes in its investment policy for which a vote is required by Section 13 of the Investment Company Act of 1940;

·     changes in the Partnership’s charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Partnership by any person;

·      causing a class of securities of the Partnership to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association;

·      a class of equity securities of the Partnership becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Act; or

·      any action similar to any of those enumerated above.

Depending on the factors described in the preceding paragraph, and other factors that may arise in the future, the Listed Persons may be involved in such matters and, depending on the facts and circumstances at such time, may formulate a plan with respect to such matters. In addition, the Listed Persons may entertain discussions with, and proposals to, the Partnership, to other unitholders of the Partnership or to third parties.

References to, and descriptions of, the Partnership Agreement of the Partnership as set forth in this Item 4 are qualified in their entirety by reference to the Partnership Agreement, as amended, filed as Exhibit 3.1 to the Partnership’s Form 10-K, File No. 000-26091, filed on March 28, 2000, which is incorporated in its entirety in this Item 4.

(a)           As of the date hereof, GP beneficially owns, and TransCan Northern, TCPL and TransCanada own indirectly through GP, 2,035,106 Common Units.  In addition, as of the date hereof, TransCan Northern beneficially owns, and TransCanada and TCPL indirectly own, an additional 8,678,045 Common Units.  The directors and executive officers of each of the Reporting Persons disclaim any beneficial ownership of the Common Units owned by GP and TransCan Northern.  GP also owns a 2% general partner interest and the incentive distribution rights (which represent the right to receive increasing percentages of quarterly distributions in excess of specified amounts) in the Partnership.

(b)           The number of Common Units as to which there is sole power to vote or to direct the vote, shared power to vote or to direct the vote, sole power to dispose or to direct the disposition, or shared power to dispose or direct the disposition for the Reporting Persons is set forth on the cover pages of this Statement on Schedule 13D/A, and such information is incorporated herein by reference. Neither the directors nor the executive officers of each of the Reporting Persons individually have the power to vote or direct the vote of, or dispose or direct the disposition of, Common Units deemed beneficially owned by the Reporting Persons, or to dispose of or direct the disposition of, or receive or direct the receipt of, distributions with respect to such Common Units. TransCanada, by virtue of its ownership of TCPL and TransCan Northern, the sole stockholder of GP., has the sole power to elect the board of directors of GP, however, all decisions regarding Common Units owned by GP are within the exclusive authority of the board of directors of GP.

(c)           On February 22, 2007, the Partnership sold 17,356,086 of its Common Units pursuant to a common unit purchase agreement by and among the Partnership and certain

investors thereto.  Pursuant thereto, TransCan Northern acquired 8,678,045 Common Units.  Additional investors, acquired 8,678,041 Common Units.  The price per Common Units was $34.57.  There have been no other reportable transactions with respect to the Common Units within 60 days of the date hereof by the Reporting Persons.

(d)           The Reporting Persons have the right to receive distributions from, and the proceeds from the sale of, the respective Common Units reported by such persons on the cover pages of this Statement on Schedule 13D/A.

(e)           Not applicable.

The information previously furnished in response to this Item 6 is amended by adding reference to the following:

The information provided or incorporated by reference in Item 3 and Item 4 is incorporated by reference herein.

Common Unit Purchase Agreement

On February 20, 2007, the Partnership entered into a Common Unit Purchase Agreement (the “Purchase Agreement”) with certain institutional investors (the “Purchasers”) to sell 17,356,086 common units at $34.57 per common unit for gross proceeds of approximately $600 million in a private placement (the “Offering”).  The Offering closed on February 22, 2007.  TransCan Northern acquired 8,678,045 common units for approximately $300 million.  Pursuant to the Purchase Agreement, the Partnership agreed to indemnify the Purchasers, including TransCan Northern, and their respective officers, directors and other representatives against certain losses resulting from any breach of the Partnership’s representations, warranties or covenants contained therein.

Registration Rights Agreement

In connection with the Offering, the Partnership entered into a registration rights agreement (the “Registration Rights Agreement”) dated February 22, 2007 with the Purchasers. Pursuant to the Registration Rights Agreement, the Partnership is required to file a shelf registration statement to register the Common Units issued to TransCan Northern within 30 days, and use its commercially reasonable efforts to cause the registration statement to become effective within 90 days of the filing of the registration statement. In addition, the Registration Rights Agreement gives TransCan Northern piggyback registration rights under certain circumstances. These registration rights are transferable to affiliates and, in certain circumstances, to third parties.

TC PipeLines, LP Partnership Agreement

GP, as the sole general partner and a limited partner of the Partnership, and TransCan Northern, as a limited partner of the Partnership, and all other limited partners of the Issuer are party to the Partnership Agreement.

Cash Distributions

Pursuant to the terms of the Partnership’s Partnership Agreement, the Partnership intends to make minimum quarterly distributions of $0.45 per unit per quarter, or $1.80 per unit on an annualized basis, if the Partnership has sufficient cash from its operations after the establishment of cash reserves and payment of fees and expenses, including payments to GP in reimbursement for all expenses incurred by it on the Partnership’s behalf. In general, the Partnership will pay any cash distributions made each quarter to its unitholders in the following manner:

·      First, 98% to all units, pro rata, and 2% to the general partner, until each unitholder has received the minimum quarterly distribution of $0.45 per common unit for that quarter;

·      Second, 85% to all units, pro rata, and 15% to the general partner, until each unitholder has received a total of $0.5275 for that quarter;

·      Third, 75% to all units, pro rata, and 25% to the general partner, until each unitholder has received a total of $0.69 for that quarter; and

·      Thereafter, 50% to all units, pro rata, and 50% to the general partner.

Voting

Each holder of common units is entitled to one vote for each common unit on all matters submitted to a vote of the unitholders; provided that, if at any time any person or group, other than the GP and its affiliates, owns beneficially 20% or more of all common units, such common units so owned may not be voted on any matter and may not be considered to be outstanding when sending notices of a meeting of unitholders (unless otherwise required by law), calculating required votes, determining the presence of a quorum or for other similar purposes under the Partnership Agreement.

Limited Call Right

Pursuant to the Partnership Agreement, if at any time GP and its affiliates hold more than 80% of the then-issued and outstanding partnership securities of any class, GP will have the right, but not the obligation, which it may assign in whole or in part to any of its affiliates or to the Partnership, to acquire all, but not less than all, of the remaining partnership securities of the class held by unaffiliated persons as of a record date to be selected by GP, on at least 10 but not more than 60 days notice. The purchase price in the event of this purchase is the greater of: (i) the highest price paid by either of GP or any of its affiliates for any partnership securities of the class purchased within the 90 days preceding the date on which GP first mails notice of its election to purchase those partnership securities; and (ii) the current market price as of the date three days before the date the notice is mailed.

Voting Rights

The Partnership Agreement sets forth the voting rights of the partners of the Partnership (including TransCan Northern and GP), including, among others, those for the removal of GP as the Partnership’s general partner, the transfer of the general partner interest in the Partnership and the transfer of the incentive distribution rights in the Partnership.

Registration Rights

Under the Partnership Agreement, the Partnership has agreed to register for resale under the Securities Act and applicable state securities laws any Common Units or other partnership securities proposed to be sold by GP or any of its affiliates or their assignees if an exemption from the registration requirements is not otherwise available. These registration rights continue for two years following any withdrawal or removal of GP as the Partnership’s general partner. The Partnership is obligated to pay all expenses incidental to the registration, excluding underwriting discounts and commissions.

The foregoing description of Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer does not purport to be complete and is qualified by the Purchase Agreement and Registration Rights Agreement attached as Exhibit 10.1 and 4.1, respectively, of the Partnership’s Form 8-K filed on February 23, 2007, and the Partnership Agreement, as amended, filed as Exhibit 3.1 to the Partnership’s Form 10-K filed on March 28, 2000.

The information previously filed in response to this item is amended by adding reference to the following new exhibit(s) filed in this Amendment No. 4:

Exhibit C:              Credit Agreement dated as of February 16, 2007, by and among TransCanada Pipeline USA, Ltd., TransCanada Corporation and the certain lenders named therein.