It's an incongruous question. Hyperloops between Basel, Bern and Zurich would make them into one virtual Mini-City. The loops would also reduce density in the travel corridors preventing a California catastrophe kind of sprawl inbetween.
The necessary tunnels for Basel would probably cost less than this:
https://en.wikipedia.org/wiki/Gotthard_Base_Tunnel
But Bern<>Zurich is the SBB's bottleneck.