Moody's Investors Service placed Gas Transmission Northwest Corp.'s (GTN) B2 senior unsecured ratings under review for possible upgrade after the company on Wednesday announced its proposed sale to TransCanada Corp. for $1.5 billion, including assumption of $500 million in debt. TransCanada PipeLines Ltd., which has agreed to acquire GTN from bankrupt National Energy & Gas Transmission Inc., holds an A2 senior unsecured rating. GTN is not in bankruptcy, but the sale will have to be approved by the bankruptcy court and by federal regulators. "NEGT's bankruptcy proceedings the court-sanctioned auction process and the approval of the NEGT plan of reorganization lend uncertainties, including whether another bidder will prevail in the auction, what the final sale price will be, and if and when the requisite approvals will be granted," Moody's noted. "The conclusion of the review will depend on the timing of these processes, which are expected to ex