Switch the coaches to biodiesel/electric and then we have something worth considering. That is proven technology and available today.
Wind and solar are great and free. Nuclear fission requires a rail-gun setup to send the waste into the sun.
In that case it would be great. Or a breeder that does not create a waste problem is also a great idea. We're at the bleeding edge of that tech.
Current transportation systems between cities is too darn slow.
If we use a faster system, say 300 mph, then we can do the same for cars as for mass transit. Building the rails for one is like building the rails for the other. I'll take a private car any day. Hands-free on the rail.
There never is a need to worry about Kwh if the source is free as in sun and wind.
And home built vehicles of any type are legal in most locales.
Mass transit is dead. It just doesn't know it.