XBLA / PSN / PC game will be released later in the month, it hasn't been revealed yet how that game will unlock the BL2 stuff.
It will more than likely be like the dollar skins. An update, and a purchase unlocks it in your list.
To be clear: It's probably going to be in a small update ahead. And will be unlocked when you buy the Poker Night game and unlock it through there. --- History is written by those who have hanged heroes.