That's not a terrible idea but once again you run into the issues of reliability and budget. At the end of the day you need to convince city officials to spend what little money they have remaining in their budget on your new system because it offers a greater value than all of their other proposed upgrades to the city AND that what you have is as reliable or better than the current system they have in place. This means asking them to trust a small company they've never heard of to manage the transit systems for their city and potentially drop contracts with companies that they have been working with for a very long time (remember this is politics). Also keep in mind that software or hardware failure in these systems could result in multiple fatalities. I'm not trying to be a naysayer, it's just important to recognize that getting something like this implemented is not as easy as convincing consumers to try/buy your product.

The best bet would probably be to get a forward-thinking city to experiment with this in a small area and then go from there.

This sort of local development work sounds like a project for Bill Gates.