Ubisoft has just a while ago congratulated to all the Playstation 3 Beta Tester of Assassin's Creed: Brotherhood on the game official Facebook page for successfully unlocking the Alliance mode.
This means that now Alliance mode in Assassin's Creed: Brotherhood is now available for all the Playstation 3 beta tester. Here is what Ubisoft wrote on official game facebook page:
Congratulations dear Beta players you have successfully unlocked the Alliance mode! Please give us your feedback on the official Beta forum!