Seems to be the big problem with this. I can't see it being anywhere near a high speed train. The distances between pods would have to be (very) significant and

Seems to be the big problem with this. I can't see it being anywhere near a high speed train. The distances between pods would have to be (very) significant and the pods themselves will be pretty small I bet as it's in a pressurised tunnel. Other problems include branches and junctions which normal railways can do with no problem.