No SIM unlock required. When it boots there is a warning that the SIM is from an unknown source, that's all. The APN for data services auto provisioned from the SIM.
Google services sign in will fail and need reauthenticating.
Here is the kicker...no re editing of the NVM is required for full VZW service with LTE SIM replaced.
This edit supports either authentication ,mode.
It just works!
It should work exactly the same for an ATT SIM.
Digital alchemy for the Droid and beyond.