While there are ways to SIM unlock the Samsung Galaxy Nexus, it is a bit harder to keep it unlocked when you change ROMs or perform a factory reset. There’s terminal emulator stuff you’d have to do and applications to install every time. While the workaround is perfectly acceptable for most, for others it’s permanent SIM unlock or nothing. XDA Forum Member jup007 has been working on a method to accomplish this with limited success. It is nowhere close to stable yet, and as jup007 says:
This is just a theory in progress. I don’t recommend anybody to try this, since it’s only been tested on my phone. Above all, backup. And as allways, I am not responsible for anything, I don’t even exist, etc…
But it can only be proven by others testing it. If you are brave (or crazy), please provide feedback. This theory can only be proved/disproved if we know that it works and limitations.
So before giving it a shot, be sure that you know what you’re doing, are aware of the risk and understand that you hold responsibility. The method is long and requires many commands to be carried out in shell. There are a few for whom the process has worked, including XDA Elite Recognized Developer netarchy. However, the process is not by any means stable, so keep checking back for updates if you’d rather wait.
More information can be found in the original thread.