Apple, AT&T sued for lack of MMS capability
tgdaily.com
tgdaily.com
So only partial: the suit against AT&T makes sense (especially if they're advertising it…), again Apple not so much.
When they first introduced the iPhone, they didn't have the leverage the do now.
Verizon and Sprint are in CDMA, not GSM… in the US, that leaves T-Mobile I think, which could run iPhones (unless a separate CDMA hardware is created).