The Google Nexus One is already compatible with many 3G networks including T-Mobile but there are a few network operators with different 3G frequencies.
AT&T and Rogers Wireless in Canada use different 3G frequencies to some operators, well now you will be happy to know over on the Google Store the Nexus One is now available with either AT&T or Rogers.
The Google web store has now an additional version of the HTC Nexus One and can be purchased unlocked with no service plan what so ever. This new addition can be used with most GSM operators globally as well.
For more information, please visit Engadget or PCWorld, or you can go direct to the Google Nexus One site here.