It's not the radio, it's the load you're using. The radio has NV in it that has your MDN (phone number) and MID (a relative of it, but not the phone number) along with the PRL. All that has to be there and the phone has to know what it is. If you have a RUIM slot then that stuff is in there. But in ours there's no slot, so it's in NV.
If the code is built to use only an RUIM, like a SIM, then it won't come up because it doesn't know to ask the radio for the information. You can make voice calls and send text messages because the radio is working, but Android will refuse to go into data mode until the subscriber information is known to the device - which means the radio has to be in one of those two states or it won't attempt to bring up a data connection.
I assume the reason it allows voice calls is so you can call 911 without being authenticated.
Motorola's radio code in this thing is well-beyond "squirelly"; it is sending up state codes that are blatantly wrong. I had to hack around this in the CM7 software to get data to work on there, and I assume the same thing will apply to this version.