Teachers' plans $84 million NuVista investment

TORONTO - Ontario Teachers' Pension Plan Board (Teachers') today announced it has agreed to subscribe for six million units (the "Units") of NuVista Energy Ltd. ("NuVista" or the "Company") at a price of $14.00 per unit to be offered by way of a private placement (the "Investment").

Each Unit is to comprise one common share in the capital of NuVista ("Common Share") and one-half of one common share purchase warrant ("Warrant") of NuVista. Each full Warrant would entitle Teachers' to purchase, within 365 days from the closing of the investment, one common share of NuVista for an exercise price of $15.50, subject to the usual adjustment provisions.

Teachers' investment is to be made in connection with, and conditional upon, the strategic merger of NuVista and Rider Resources Ltd. This merger transaction will see Rider shareholders receiving 0.3540 of a NuVista common share for each Rider common share. Teachers' obligation to complete the NuVista investment is conditional upon, among other things, the merger being approved by a majority of the NuVista shareholders, who vote at a shareholders' meeting, the successful completion of the merger, and the receipt of all necessary regulatory, stock exchange and third-party approvals. The merger transaction is expected to close in March 2008.

Teachers' currently owns 5,157,246 common shares of NuVista, or approximately 9.8% of the outstanding Common Shares. When the additional six million unit investment and the merger are completed, Teachers' will own 11,157,246 Common Shares, or 14,157,246 Common Shares assuming the Warrants are exercised, representing approximately 14.2% and 17.4%, respectively, of the outstanding Common Shares based on the current estimate of shares to be issued pursuant to the completion of the merger transaction. (Immediately following the Investment, Teachers' is deemed under the early warning provisions of the applicable provincial securities legislation to beneficially own and control 14,157,246 Common Shares, representing approximately 22.9% of the outstanding Common Shares calculated on a partially-diluted basis (allowing for conversion of the Warrants but not of any other outstanding convertible securities of the Company or any Common Shares to be issued pursuant to the completion of the merger transaction between NuVista and Rider Resources which is a condition of Teachers' obligation to complete the Investment)).

Teachers' has subscribed for the Units for investment purposes only. In fulfilling its responsibilities as an owner of securities, Teachers' may make its views known to the Company's management or board of directors when proxies are solicited and on other occasions. Depending on market conditions and other factors that Teachers' may deem material to its investment decisions, Teachers' may in the future acquire Common Shares, Warrants, options or other debt or derivative securities, in the open market or in privately negotiated purchases or otherwise, and may also, depending on then-current circumstances, dispose of all or a portion of the Common Shares, Warrants, options or other debt or derivative securities, in one or more transactions, in each case to the extent then permitted by applicable law and regulation.

With over $106 billion in net assets as of December 31, 2006, Ontario Teachers' Pension Plan is the largest single-profession pension plan in Canada. An independent organization, it invests the pension fund's assets and administers the pensions of 271,000 active and retired Ontario teachers.

This news release is being issued under the early warning provisions of Canadian provincial securities legislation. For further information a copy of the Early Warning Report that will be filed with the applicable securities commissions can be obtained by contacting:

Contact:

Deborah Allan
Director, Communications and Media Relations
Ontario Teachers' Pension Plan
(416) 730-5347
deborah_allan@otpp.com