In a joint bidding scheme, does the City have to prove that there is no additional expenditure of public money as a result of the joint bid scheme?

For example, the City argues that there is no additional expenditure of public money as a result of the joint bidding scheme (see, Matter of Signacon Controls v. Mulroy, 32 N.Y.2d 410, 416, 345 N.Y.S.2d 527, 298 N.E.2d 670, supra ["A contract which provides for a lesser income to the governmental unit than a competing contract might provide, is an 'expenditure' within the meaning of section 103."] ). Its argument is premised on the "commitment letters," by which the utility companies agreed to reimburse the City for the differential between the lowest bid for City work and the cost of City work in the accepted lowest joint bid. We perceive a considerable hole in this purported security blanket, both legally and practically.