I seem to be having the same issue as what you're experiencing. I have unlocked G2 that I'm using on Koodo network. Just last night my phone switched to emergency calls only. It was working perfectly fine for a whole month. And before that I was using the phone on Fido network with no issues.
Some additional info. I tried my friend's Roger's sim card on my phone and it showed emergency calls only. When my friend tried my sim, he was able to connect to Koodo network.
On my phone when I search for networks, it does find Koodo, Rogers, Bell networks. It just doesn't seem to be connecting for some reason.
My phone is stock, not rooted. I wasn't even doing anything out of the ordinary with my phone so I have not idea why this happened all of a sudden.
I tried the hard reset also and that didn't work for me either.
Not sure what else to do. May look into custom rom but not sure if that's going to work..
What I found out is that my phone had been blacklisted... which means that it had been reported lost or stolen by somebody else and the IMEI number had been reported. The phone became useless... and as one of the guys that i brought it to said, i essentially had a very expensive paperweight. hope your situation turns out better than mine!