Isn't that great!?!? but sadly it's only a few selected games like Lost Planet (By the way what's the different between Extreme conditions and Colonies?)
Colonies is basically Lost Planet + an expansion pack with extra maps, weapons, and gameplay tweaks. Also new modes and online features.
So now the games for windows live is 100% free, and silver xbox live members can TEMPORARILY play cross platform xbox games online free. (Lost Planet, Shadowrun, Universe at War)
Ahh... That's weird. You think you post here too much when you're a "Hero Member" with about a thousand votes and five stars? Hmm...?
And you can only play Colonies free cause Extreme Condition doesn't have cross platform.