The board of transportation shall attend at the time and place specified and shall publicly open all proposals that shall have been received, but such board shall not be bound to accept any proposals so received, but may reject all such proposals and readvertise for proposals in the manner hereinbefore provided, or may accept any of such proposals as will, in the judgment of such board, best promote the public interest, and grant a franchise and execute such certificate accordingly, subject to the approval of the board of estimate and of the mayor.
N.Y. Rapid Trans. Law § 46