HTC Hero and G1 T-Mobile USA Compatibility

[Inept]

Alright, I used the search feature to check and see if this has been posted elsewhere but sadly it has not. I am a T-Mobile USA customer and a happy owner of a G1 Android phone. Would it be possible for me to purchase an HTC Hero or G1Touch from a 3rd party and unlock it to work on the T-Mobile USA 3G network with my G1 SIM card?

Thanks in advance