I agree with the Klingon prison break-out, and that its likely a mining ship. I think, however, that they use a slingshot maneuver to go back in time, using a star near the Klingon border. When they pop out in the 23rd century, the USS Kelvin just happens to be in the way. This would also explain the presence and destruction of the 47 Klingon warships apparently on the same day.
That's what I think. Add this to the last scene in the trailer "The wait is over," and I think this is his escape from prison. I'll guess his peeps break him outta "the rock" and they steal a mining vessel tricked out with one of those Klingon time travel devices like Janeway had. That'd 'splain the drill over Vulcan and how Romulans have time travel. Strictly speaking they don't, unless the steal it from Klingons, whom we know do have it (from Voyager, Endgame). The Hentai shipis probably a giant Klingon or Reman mining ship, thus the drill and weapons too (because Klingons in particular would never leave anything unarmed).
Someone did a toy report awhile back and mentioned they saw Nero's ship (this could have been at Trekmovie.com...), that unlike Spock's 'time ship' Nero's ship doesn't do time travel on its own - so a slingshot makes sense.
Sharr
