Edited to add: My question was primarily legal - if someone were to step up and demonstrate this was feasible could it possibly make a difference?
> I understand they're in the planning stages, and I don't think it'd be absurd to say "this is a train, just better and cheaper".
This is a hypothetical concept, while HSR is a widely demonstrated, well-established technology, with real vendors with proven situations. There's a lot of civil engineering to go into building the infrastructure, but the technology is there (and isn't still looking forward to "[s]ub-scale testing based on a further optimized design to demonstrate the physics", as is the case with hyperloop.)
Hyperloop as an alternative to HSR is about in the same situation as nuclear fusion as an alternative to wind (or nuclear fission) power. .
But frankly if the project polled well enough, you might be able to make it a reality.