I'm not from familiar with Miracast. All I know is what the Wiki
page said. It really reads like DNLA. And from my experience, this has been something that can be app dependent. Since I have no experience with Miracast, I don't know if it's full mirroring or just certain apps.
That said, Miracast may just be work versus just installing individual apps. Unless there is something in the application code for specific devices, if you side load an APK, it should run on the Ouya. Doesn't mean it will run well or look correct. Thus, you may be able to just side load XBMC. I know I'll try it with Plex, Netflix, Hulu, various sports--MLB, NHL, NBA, etc--and so on.
I couldn't figure out what the end result you were suggesting about friends coming over and their mobile devices.