Standardize the pylons (tubes)by government fiat and give away the right of way along the highway and let private enterprise build it and run it.
If you think about it that makes it much like the airlines. The gov sets the air corridors and private enterprise built the rest.
I'm not saying that it necessarily would work but it's got a shot at replacing short haul air and won't cost the taxpayer a Penney.
Excuse me but hey gave away 640 acres of land along rail roads in the 1800’s and that has failed. Why do we want to fail again? Lots of interstate highways were built with space for rail roads but there are no takers. You can only force a company to do something so long as they still have money.