[VandyILL]

One of my takes on it is that it has to be some sort of land/underground interconnection between cities.

My reasoning behind this is that he is open sourcing the designs. My guess behind this is that if it is a ground based system that requires right of way/property access etc. then there is tons of transaction costs & government regulation that would prevent copy cats from destroying the first mover's capital investments that would normally be protected via IP law.

If it didn't have these high transaction costs associated with it, then any actor could come and undercut your system after the tech behind the open source designs becomes cheaper. Traditionally this would be protected because of IP laws. However, he's dismissing this route & letting anyone up to the challenge take on the construction challenge with him. I'm guessing this is likely because the government won't eminent domain/allow/permit etc. extra routes between SF & LA etc. if there's already a hyperloop.