There's no information in the press release on the game's arrival on XBL.
The game will retail for $19.99/ £15.99. Missions will be retooled to bolster the pacing and challenge, and Aveline’s Personas have widened its presence, with missions in the game specifically tweaked for them.
Lastly, if you purchase a season pass for Assassins Creed 4: Black Flag on Xbox 360, you will get a 25% discount on Assassin’s Creed Liberation HD. Which is not so bad.