Update: We're going to pull this back a bit. So far the FCC has posted a trio of reports this morning for the Nexus One but the outcome is inconclusive based on our own continued research and from the discussion in our comments. According to the bands listed (I, IV, and VIII) we're definitely looking at a T-Mobile USA device as well as applicability on European networks (among others). The whole AT&T range is in doubt as the test lab incorrectly lists 815-880MHz frequencies as part of band VIII. Hold tight as we dig deeper.
Update 2: Only WCDMA Band IV was tested in the Part 22H / 24E / 27 Report, leading us to believe that the Nexus One is going to be HSPA 900 / 1700 / 2100 (a pretty common tri-band 3G setup) plus quadband EDGE. Sorry, AT&T, but that's how the cookie crumbles.