Are you? I wouldn't rule it out, but personally I think getting an outside signal into a sealed capsule which is moving so rapidly that it must use battery power rather than a physically connected power source seems more than trivial.

Nah, wifi would travel great in a long metal tube.

For 300 miles? Or are you proposing spacing hubs out along the journey, in which case, wouldn't frequent reconnection be an issue?

You can yak on your cellphone (or watch movies on your tablet) for the entire 35 minutes of this journey.