Except it doesn't matter if their only "innovation" is normalizing using sewer tunneling type equipment with sewer tunneling type costs. That's a MASSIVE advantage over the insane costs we have for tunneling projects in the US.

To me, seems the real problem is, why are tunnels built in the US orders of magnitude more expensive than tunnels built literally anywhere else? It's a people problem, not a technical one. There are plenty of tunnel projects around the world that are in my opinion far more valuable than shuffling around private cars (the scale of public transit through such tunnels is many orders of magnitude more impactful). But until the US gets its labor costs in check building infrastructure is poor cost-value ratio there.