The fact remains that there are often economies of scale to be had. Not ever transit system can buy cars 400 or 500 at a time, like an NYCTA for example. But if 2 or 3 cities can get over their need to have their very own car design and pool their orders for similar or same cars (with the paint job and logo being the biggest difference) into very large orders, then the engineering and re-engineer costs go down, as do the tooling costs for the manufacturer.