> It seems like this tunnel is better thought of as a tech demo that will be open to the public.
Except it sucks as a demo.
TBC is basically proposing a variation of Personal Rapid Transit. The main theoretical virtue of PRT is that it provides a point-to-point mass transit system; its main theoretical issue is that it is low capacity for the cost of its infrastructure. Demos should showcase strengths; if you're proposing improvements to technology, you should highlight your ability to overcome previous limitations.
This proposal does not highlight its capabilities, and gives ample room to excuse failures. It is planned to be single track: capacity will be utter trash. Point-to-point is pointless when there's only two points.
Of course the worst aspect is that the one-way, bursty nature means you need to have someplace to store the cars at each endpoint. It's not bad at a stadium, which is naturally going to be a massive dead space, but the other terminus is supposed to be a metro station. Either you're going to need to build a massive underground cavern (at which point boring a second tunnel and deadheading cars to empty space would be much cheaper [1]), or you're going to have to dedicate surface space to car storage--at a metro station, where logic dictates you should be having high density for commercial/residential purposes.
[1] The cost of subway lines is heavily dominated by the stations that need to be dug along the route. I haven't sized out dimensions, but it's not unreasonable to assume the necessary car storage is going to be larger than an underground mezzanine.