-Tomb Raider 2013 was at MS' E3 presentation. Correct me if I'm wrong, but that wasn't the first time MS has gone out of their way to specifically feature the series on stage at e3.
-Crystal Dynamics have developed exclusive content for previous Tomb Raider games with MS.
-360 was their goto platform last gen, while they delegated the PS3 ports to another developer.
-MS even featured one of the a Tomb Raider release as one of the XBLA Games of the Summer, where it was released ahead of the other versions on 360.
-MS have done co-marketing with them in the past few TR games.
Anything you remember about them and Sony was back in the PS2 days.