But, also, in the detailed part of the proposal, he points out that with high densities (e.g. NY city) you need so many maglev cars to meet peak demand, that parking them off-peak is a significant problem.
Yes, but they could probably be automatically parked in tightly packed parking lots far out of town. As peak approaches, they could drive themselves back into town.
Because the customer doesn't require a specific car, these parking lots can be FIFO queues or FILO stacks and won't require maneuvering space.
Also, the cars could transition to a much cheaper, non-maglev parking system. This might even be done using a robot to lift and store the car into a slot in an otherwise "dead" grid. One expensive robot that can move in 2 dimensions and a lot of simple steel rails is a lot cheaper than heaps of maglev track.
Finally, the 333k car estimate was based on a subway where there is only one place that people are leaving from. There was an assumption that EVERY car must return EMPTY to the source of the trip afterwards to pick up the next passenger. This is not true, the percentage of returning cars is probably much lower (30%?) And even those cars could be useful for part of this trip.
But, also, in the detailed part of the proposal, he points out that with high densities (e.g. NY city) you need so many maglev cars to meet peak demand, that parking them off-peak is a significant problem.