[bluGill]

We can do it in the ISS. Not an easy problem, but it is a solvable problem. The problem is all the solutions will cost a ton of money.

[avianlyric]

The ISS isn’t kept at a vacuum and isn’t hundreds of kilometres long, and space needs no assistance from us to maintain a vacuum, gravity’s got that covered.

[bluGill]

The outside is a vacuum, the inside is at pressure. While the forces are reversed, the problem is otherwise the same.

[tsimionescu]

The ISS is not a tube hundreds of kilometers long, so I have no idea how this compares. Also, the ISS doesn't require pipes, and can easily have many segments which are airlocked from each other, which a high-speed train would not do well with.