Interesting writeup about the 112 trick used by upcoming SIM interposer: http://is.gd/HwzKq9
(summary at end)
What does it mean to unlockers?
1.It works if A.your network handles 112 calls properly according to the GSM standard; B.they are tolerant to TSMI spoofing and does not actively validate your SIM again for incoming calls.
2.Unlike its ancestors, the i4 SIM interposer is not a drop-in-and-forget device. The exact precedure must be performed should the device restart, lose reception for an extended period of time or move to another PLMN. In all these situations the TMSI expires and has to be obtained again. Theoretically it is possible for a daemon to automate the process similar to ZeroG, but that only makes thing more convoluted. GO TO THAT LINK AND READ MORE