Cross-platform MMOG for Next XBox?

Team XBox has an interview with the producer of Huxley, which will be a massively multiplayer first-person shooter for the next version of the XBox. Apparently the game is being built around the Unreal 3 engine, and early screenshots of it are quite impressive. What I found particularly interesting, however, is that XBox users and PC gamers might be able to partake in the same persistent world. "We are developing a PC version of Huxley. We are also considering the possibility of allowing XBox 2 and PC gamers to play together. We’re not sure if cross-platform play will work without any problem yet. Nevertheless, we trust Microsoft’s XNA."