Yeah, I'm very sceptical of anyone being able to maintain a near vacuum for a freaking train. Sure, they might be able to do it, but only for bragging rights, not for any practicality
I also think it will be incredibly difficult and maintenance intensive to keep any structure that size at near vacuum.
I think there may be a break even point between cost and effect where removing enough air to reduce (but not even close to eliminate) drag is worth the trouble though. Very large clean zone manufacturing facilities are routinely kept slightly above outside ambient pressure to prevent dust/moisture/insects from getting in.