How many charging stations will be available? At what cost?

The fuck are those questions? You want a detailed roll out plan for a hypothetical city? No know I can’t answer that question with any useful details. It’s going to be different for every city, but as many as necessary.

And if they are fought against by cities fully invested in.mass transit

Why would a city that already has mass transit plans need a full on e-bike plan? But even with busses and trains, limited e-bikes can still be useful for people who can’t work on a schedule, the mass transit path is inconvenient, or live far enough away from the bus/train stations and want to e-bike to them.

who covers the costs to clear that up?

The fuck is this? E-bikes aren’t forever. The bikes and charging stations require maintenance and repair. If you want to discontinue them, just come up with a sunsetting plan. Who pays for them? Either the state via taxes or a private entity. Citibike is already planning e-bike rollout. Just follow that model.