I think relevant to this might be the question. Are micosoft servers p2p or standard? Is it possible to play in the same instances between two different server structures? I really don't know.
Braben's comment seemed to be about the upgrade procedure rather than the server config. If both versions share the same universe they also need to share the same client version; and Frontier can't control the Xbox client's upgrade process directly. So they had two options:
- delay each Mac & PC update until the corresponding Xbox update has gone out. (Annoys the Mac & PC players, waiting longer for versions to be released, plus longer downtime waiting for the Xbox version to pass through the MS update process)
- put the Xbox client (and any other client for which Frontier don't control the update process) in separate universes.
I'd guess it would be the same if ED was on the Mac App Store - not sure about Steam and how it pushes out app updates.