I'm guessing it'll be a custom UX Config.xml thing maybe using "PC Games" instead of HomeBrew as a lot of those are PC ports to the Xbox. There's some really good ones amongst a wider selection of games that either do not play that well or remind you how lucky we are as gamers not being back in the 1980s.
In the same way that menu option could also be a direct launcher of the ScummVM 'emulator' which supports a limited number of old school point and click PC adventure games which do run reasonably on the Xbox eg. Broken Sword.
It'll be interesting to know more.
However no way will PC LoK: Soul Reaver run on the Xbox. Even using the Playstation PCSXbox emulator I think you'll be lucky to get anything approaching playable performance.