It works if you preserve your baseband using tools such as Snowbreeze or Pwnage Tool.
I'm currently on iOS 5GM and it works, the only different thing is how to activate it.
This worked for me:
- While your phone is ON, remove the sim, so you will get the NO SIM message
- Turn OFF your phone (DON'T INSERT THE SIM YET)
- Turn ON your phone and wait it to boot. "No sim" message will appear.
- Insert your Sim tray with gevey sim
- Wait some seconds till the gevey sim message pops up and dismiss it
- Wait for "NO SERVICE" and Dial 112. Hang up after 2-3 seconds.
- Toggle (on/off) Airplane Mode. "Sim Failure" message will appear, Accept and Wait for 10 seconds.
- Toggle (on/off) Airplane mode again. Another "Sim Failure" message will appear, now wait until "NO SIM"
message appears (may take some seconds).
- Toggle (on/off) Airplane mode again and wait for your Signal and you're ready to go!