I got a little lucky when the initial whitepaper was published because there was a top level comment from someone in construction logistics that said something like...

"I can't speak to anything else in here, but the listed costs for the installed concrete is only 10% what it should be. If Elon Musk has found a way to install concrete 10x better than everyone else he shouldn't be building a train, he should be taking over construction globally."

Just an immediate splash of "oh, this is BS" cold water.

It's 73 miles from Austin to San Antonio "as the crow flies". The Vegas Loop took two years to build 1.7 miles of tunnel [1]. So we should expect this to be complete sometime around ~2088.

[1] https://en.wikipedia.org/wiki/Vegas_Loop

People still fall for this monorail scheme?

Elon may "live" in Texas but he didn't do his homework.

I'd be willing to bet the geography won't allow such a line underground. Texas is full of caverns, oil, and underground gas.

This small physical constraint sits on top of (underneath?) the rest of the reasons it's ridiculous.

I guess it will be ready for the Austin/San Antonio Olympics of 2040.