So, how most older rails and subways work is with an immense amount of power, and one of the rails is powered. Hence why touching both kills people because you complete the circuit.
Technically since this more futuristic, they could be more modern rails. Just tracks and the actual engine supplies the power. (Solar isn’t going to work underground).
So if it was the first version, there’s no working power grid in cata. The infrastructure seems to have been destroyed or it’s no longer kept up, because all of the workers that did work in the various power plants, are dead.
I don’t see why there couldn’t be some rails, and like a few subway cars, and a few hundred zombies from those that were on the train when it last stopped though.