Aside from it being built by tech bros, i actually like this. It could serve a purpose similar to public transport like car sharing (not carpooling) and rental bikes. This would be far from as efficient as regular trains or street cars, but those modes of transports need volume. As soon the population that uses the rail decreases to a point it becomes to expensive to run a train every one or two hours, often the expensive physical infrastructure remains while the service disappears. In those cases i could totally see this being a better option than heavily subsidising or totally removing trains on that section of rail. But to be honest, I can't imagine there are enough of those places on earth carry the costs to develop this tech, also because these cars are only the best fit if the abandoned line is a single track line.