Recently a group of Canadian devs got the inert 4G chip working on part of the 4G spectrum after using the Google Nexus 4 factory images. They were subsequently pulled from the Google Developers page, probably because of licensing concerns from the chip makers.
Anyway they are now back so if you are looking to get your Nexus 4 back to a factory fresh state then you can get them from developers.google.com/android/nexus/.