I think the demand would come after it gets built. Even bigger would be demand for Bern/Zurich and Basel/Zurich in 30min, bringing these cities comfortably into commute distance. People do that today but only if they really must.
There is an aspect of Swiss economy that makes HSR attractive: high degree of decentralization.
Those cities already feel close enough together. More to the point, I don’t think Switzerland probably wants the kind of growth that HSR would enable and encourage.
No they really aren't close enough together. For example, I know someone who moved from Zurich to Olten so that their girlfriend's commute to Bern would be reasonable. Now you have 2 people with 50 minute commutes instead of 1 person with 1h45 and another person with 15min. If there was a 30min connection from Bern to Zurich it would be perfectly reasonable to live in one and commute to the other.
Again, does Switzerland really want to become one big mega city? It is up for the Swiss to decide, but a huge commute draw between Bern and Zurich (or even Bern and Lausanne) would lead to something more like Japan.
Maybe that’s just me but I don’t think of Japan as a bad model in how to have a dense population that is prosperous. If anything their biggest problem currently is depopulation of remote areas.
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.
Basel<>Bern (direct) would need tunnels.. The other 2 routes are pretty flat. Most of the Swiss economy is in the valley between the Jura range and the Alps.
The necessary tunnels for Basel would probably cost less than this:
There is an aspect of Swiss economy that makes HSR attractive: high degree of decentralization.