I don't see much difference between a more affordable autonomous bus or van option vs a subway. The benefit will eventually be access to the tunnels more than the fact it's large and on a track. But in cities it's also incredibly expensive to build anything without a hundred stakeholders interfering so a large amount of new tunnels is probably DOA just like most high speed rail projects have been.
Fan cars are old. Nothing about them is new or special or unique. Trying to build infrastructure dependent on such a feature would be the dumbest thing since monorails.
Just build subways for heaven's sake.