Whats more awesome than Chris Squire? Chris Squire playing with Jimmy Paige.
So i guess after John Bonham passed away Jimmy and Chris were living in the same area together and Jimmy would sometimes come over to Chris's place and help him record demoes because he was bored. Eventually they started jamming together on a regular basis and decided to start a band. Chris brought in Alan White and started rehearsing (and Jimmy asked Robert Plant to join but he refused saying the music was too complicated). XYZ stood for Ex-Yes-Zeppelin.
Sadly the project was short lived and drifted apart. They never officially released anything. I can actually see why, Jimmy doesn't really gel with the other two guys, being a blues-rocker rather than the prog-rock virtuosos that the other guys were. Still, it would have been awesome if they'd kept at it. Here's one of the songs they recorded in their short time together: http://www.youtube.com/watch?v=sykd7S4dxEw
Chris did lead vocals on all the recordings except the instrumentals.