A single contractor was to be chosen to develop two X-vehicle prototypes.
In most other states, such jobs are awarded to a single general contractor, who can then hire subcontractors.
The city would choose a single contractor to provide pay toilets, newsstands and bus stop shelters.
A single European contractor, he said, would "essentially not be competitive."
Besides, if sales kept growing, the business would eventually be too big for a single contractor.
The aim was to bring all three projects under a unified umbrella, administered by a single prime contractor.
New Jersey and Connecticut allow the option of a single or multiple contractors.
The law allows them to negotiate contracts directly with public agencies, instead of having to go through a single general contractor.
The report said that a single general contractor could have forced the subcontractor to do the job by withholding payment.
Many weapons, including tanks and nuclear submarines, are already produced by single contractors.