Daily Radar HBO got to this one first.

Xtech has announced a product that will enable Xbox and PlayStation2 online gameplaying capabilities via dial-up Internet connections. Details on the product will be revealed in the coming weeks. Meanwhile, Xtech will say only that the vast majority of users still use narrowband accounts for online gaming, and they're being ignored by next-generation consoles that are shipping as broadband enabled only, so it is aiming to bridge that gap.

Conceivably, this could be used as a connecting solution, paired with the New Millennium gaming network. It would be interesting to see what would happen in that eventuality. Probably a bit more lag than some would like... no offense to the dialup users out there. (I was one of them until just recently)