This is very, very wasteful compared to actual mass transit. A subway network is much more effective at delivering people.
If he's looking for mega-good, Musk would do significantly better to drop a full subway network.
edit: tunnelling is a broadly solved problem. It's difficult, expensive, slow, etc. But there's no engineering reason why a hole in the ground can't happen. Musk might be able to drive some significant improvements there. No idea. But tunneling itself is not a reason to knock an idea beyond the cost and geoengineering involved.
If he's looking for mega-good, Musk would do significantly better to drop a full subway network.
edit: tunnelling is a broadly solved problem. It's difficult, expensive, slow, etc. But there's no engineering reason why a hole in the ground can't happen. Musk might be able to drive some significant improvements there. No idea. But tunneling itself is not a reason to knock an idea beyond the cost and geoengineering involved.