Xbox has been notorious with cross server play and lifting the requirements of Xbox Live. I think some of you have seriously never played on a Xbox console, their strict requirements date back to the original Xbox, this is going to be a bit of a history lesson. When Sega released Phantasy Star Online Episode 1 and 2 on Xbox, the game was required to have Xbox Live, plus a Hunters License, it's online service fee. Sega gave the green light for this, released the game, but stopped supporting it because of Xbox wanting to charge for updates, players got annoyed at the lack of updates and eventually started to hack the game, they were able to bring over Dreamcast items, that were planned to be released in content updates, as well as found files that suggested that Sega was considering bringing over Episode 4 to Xbox as a final expansion, instead that was scrapped and it was released as Phantasy Star Online Blue Burst, as a PC only release.
Microsoft has continued to do this, and even stopped the Xbox 360 version of The Orange Box from using steam servers, they also prevented Portal 2 from again being cross play. Sony actually allowed cross play before Xbox ever did and way before any of this started to come back into the main stream with Portal 2.