Interesting...some prepaid subscribers like metroPCS or BoostMobile could do this since its inception and no restriction to receive MMS sent to Gmail inbox. Still waiting to send MMS using Google Voice.
as a sprint customer i could send to tmobile but couldn't receive. for at&t i can send and receive. for verizon neither send or receieve. other sprint customers i can only receive from them but at one point could send or receive. for boost i could only receive. By receive I mean it goes to my email .