The show discussed the need to evacuate the tunnels in order to attain a speed of 5,000 MPH. The show discussed the evacuated train tunnel in the context of mail tubes, like the ones used at the bank, or in large office buildings.
But mail tubes are not total vacuums. They work because air is pumped from one end of the tube; but normal air pressure prevails behind the shuttle. That differential in air pressure is what propels the shuttle; without that--in a total vacuum--the shuttle would just sit there. Yet the show suggested that a total vacuum is what makes the shuttle move.
And the train? In a vacuum, "the train would enter a kind of free fall!" the announcer gushed. What? "Free fall"? The only thing a vacuum will do is eliminate air resistance. That's it.
Oh my God.
They're talking about fire now. In evacuated tunnels. The cars will have to have "massive fire-suppression systems".
The show also mentioned how the train would have to deal with "acceleration". Because, you know, there's no way you can possibly control the rate of acceleration.
Oh my God, part two: now they're talking about an "aging nuclear sub" colliding with the tunnel. "The vessel weighs 60,000 tons, and carries 16 nuclear warheads!" (What do the warheads have to do with anything?) But disaster is averted: "Yes--it is a happy ending."
Why on Earth would the tunnel even be above the sea floor? Why not drive a TBM through the rock under the sea floor instead? Just use "submerged" sections for the places where they're needed.
...but considering how well-thought-out the science of this crap is, I guess looking for logic in the basic premise is a bit of a stretch.