I haven't gone looking for it. If you see a link, please report it.
Microsoft generally have a problem with leaked versions. I remember seeing leaked Windows 2000 betas (and I think even RTM) when I was at University. My suspicion is that it's not anyone at Microsoft leaking, but someone at the CD/DVD mastering houses. No evidence, just supposition.
I think you'd have to have hacked/modded your Xbox in order to play this, though, since a genuine Xbox disc is dual layer, and it's pretty expensive to obtain a dual-layer burner (if a dual-layer DVD-R would even be Xbox compatible).