This seems like technology that addresses mostly fun, theoretical problems - like traffic optimization, not ugly, practical ones like tight municipal budgets and urban sprawl.
Even in the US, passenger rail is typically run by the government or government-like bodies, while freight rail is just private companies. I don't think there's an intrinsic reason for that, it's just how it is. (More like, people with goods to transport are willing to pay, but people with only themselves to transport aren't. Or we see public transportation as a "public good" that's worth subsidizing, but of course the government super subsidizes the road network too.)
The fact that your local politician doesn't want to allocate public funds to shoring up a collapsing bridge doesn't mean that Elon Musk can't spend his own money to build his own bridge (tunnel in this case), right?
It would be relatively easy (which is to say, it would be easier than doing it to private cars) to fit the municipal bus fleet with the equipment to also become automatically piloted "packets." For that matter, it would also be possible to bake-in such functionality to Tesla cars.
If you're advocating for a private transportation network, then I'm theoretically OK with that as long as it's not subsidized directly or indirectly by the taxpayer. No special tax loopholes or favourable deals on digging rights please.
It would be interesting to learn details: How often? Who is making how much? And in what circumstances does it tend to work and not work?
During World War I, regulation prevented the rail industry from properly responding to an uptick in rail demand for exports to fuel the war's various foreign factions (ship capacity had been greatly reduced by German submarines). After the rail companies asked for a rate increase in order to help deal with the increased traffic (which was rejected), the President seized the rail network in order to sidestep the debacle and get their exports out.
The rails were de-nationalized when the war ended 2 years later. After that, the use for passenger travel steadily declined as automobile and bus transportation grew, and the rails never recovered (except during WWII). In 1971, when the entire network was about to collapse, the government created Amtrak. Amazingly, most of the network is still limited in capacity and speed due to regulations from 1947. And most of the improvements in the system have come since 2000. Any subsidies that could have upgraded the network or increased capacity or efficiency over a period of 80 years went into building highways and airport control towers (but not more efficient public buses or light rail).
Of course, Amtrak still leased its rail lines from the railroads, so the old rail companies became the new landlords and freight providers, while Amtrak serviced passengers. Amtrak basically cut passenger service and available rail lines in half, with whole corridors becoming freight-only. Later Amtrak bought bankrupted railroad track, and currently something like 25% of the rails Amtrak travels are owned by it.
The parent is half-correct. The freight customers don't have the same needs as the passengers, and "more convenient" methods of transportation exist for them, but for some reason the government demands that passenger rail remain (for the next big war?) so it got bailed out and nationalized.
It will interact with the surface economic reality in the same way that flying Audis in tunnels interact with the dystopian wilderness in Hollywood sci-fi films.
Creating a powered tunnel, especially if it can be engineered to be done faster and cheaper, could result in increased urban density?
That being said the cost is currently extremely high, the tunnel that is finished boring and still under construction is estimated to cost 4.2 billion for 2 miles dug over 3 years.
But seriously, Elon Musk appears to be dating hot and crazy at the moment. Let's just let him get through this phase of his bucket list so he can get back to being visionary once he realizes why one should never marry hot and crazy.
But I seriously doubt this thing is actually cost efficient.