[usrusr]

Both BBC quotes are in full agreement with the document at http://spacex.com/sites/spacex/files/hyperloop_alpha.pdf . Page 12, "100 Pascals", that's roughly 99.9% of the air removed.

The distinction between "very low pressure" and "vacuum" that is implied by the "hyperloop is not a vactrain" camp is a fantasy.

[shkkmo]

It is pretty relevant at the speeds being discussed.

[usrusr]

For the design of the vehicle, yes, for the design of the infrastructure, not so much. Those 100 Pa are actually much lower than what previous vactrain proposals suggested. The only difference is that hyperloop is trying to do something useful with the unavoidable trace atmosphere instead of just overcoming it.