Dunno if this is the same music but EA do sell usage rights to some sound tracks to third parties which is why you always hear the Sims music in BBC programs like The Apprentice in the UK, so it's not entirelly impossible for a game trailer to do this like a movie trailer where they use something from an old movie while the official sound track is still "under wraps".
Another possibility is that someone at Frontier accidently left a test sound track in
Or it's not the same music...
Or Frontier are just evil/lazy/whatever-the-latest-Yamiks-vid-says etc
All wil no doubt be explorered here so take your pick