Check cellzealot's posts, there is a fairly recent hack that activates the GSM in the bionic
Yep, I know it. But I have 2 devices: one of them works but on second doesn't work. I've tried 5 or 6 times switch on, but every time I just see: phone application broken. I tried twice on fist phone and exploit works without any problem.
BTW: on my Droid RAZR after official update to android 4 phone get global mode and phone works with different carriers.