The Federal Reserve Bank of New York and a unit of BlackRock Inc. kicked off a plan to dispose of assets the central bank acquired in the bailout of American International Group Inc., offering $1.5 billion of subprime mortgage bonds for sale in a Wednesday auction, according to traders. BlackRock Solutions, which is handling the widely-watched sale, on Monday afternoon circulated a list of roughly 50 mortgage securities to Wall Street dealers seeking competitive bids on the bonds.