news.com has more details here. I’d be surprised at this point if this is THE Google phone that all the recent chatter is about. It seems this is a ‘mobile lab’ for employees to dogfood some internal developments before they are released. Although the phone is unlocked and not tied to any particular carrier so there is some flexibility there, but typically unlocked phones are several times the subsidized price you get when you get a new device through a carrier with a contract.
To be honest I’m more interested in the rumors of a data plan only phone with VOIP capabilities, but there’s no compelling reason why any carrier would let you run that on their network if they lose the opportunity to milk you for voice calls.