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Nonetheless, BoyGeniusReport (which has a decent hit rate on its rumor reportage) claims that the Google Nexus One (aka "Google Phone") will be made in an unlocked version compatible with AT&T's 3G network:
"...we’ve heard from a source that there will be an AT&T 3G-compatible version of the Google Nexus One. Our connect described it as being a 'second' unlocked model, with the T-Mobile-subsidized unit being locked to T-Mobile. Our tipster was so impressed by a Nexus One in person, they said they would 100% give up their T-Mobile BlackBerry 9700 for one when it’s available."
So little is known about Google's deals with carriers that we'd urge caution on this until the Nexus One launch on Tuesday.