More on Why Dust is on the PS3

CCP Halldor Fannar had this to say while at E3 which confirms that it was Microsoft that held back Dust on the Xbox:

Let's just say that with Sony at least they have policies that allow us to build the game the way we want. - Source 

If Dust514 is hugely popular this might bring a change to the way Microsoft look at 3rd parties using live but I feel Dust will be gone 3 months after release. Such is the nature of the console gamers attention span.