I think all Nexus Ones are 900/1800 GSM. The only thing that changes is the 3G. If you mean 900 MHz 3G though, I guess it will work, since I'm using an European Nexus One. I cannot vouch for it though, so try with caution. I don't think there are differences in radios, but I can be wrong.
ALL N1's use the same radio, kernel, rom, everything. They are identical except for the radio chip which is all managed in hardware so completely independent of anything you flash onto the phone.
EDIT:
Flashed the radio, confirmed as working ok. Version reported as "32.41.00.32H_5.08.00.04"
Working fine with a recent CyanogenMod Nightly build (07122010) and WildMonks BFS 925mV 2.6.35-rc4 kernel.
EDIT2:
Speedtest gives me around 1900kbps down & 1400kbps up, which is pretty good considering my signal strength is only -85dBm. I'll try it later when I'm in a better reception area, but looks like all is well.
Bluetooth & WiFi are both working correctly as does video recording.