Google originally released the Android 4.2.1 code into the AOSP (Android Open Source Project) back in late-November and coming a bit more recently, it looks like they have since dropped in some updated code. And by updated, we mean two newly tagged files. The files are showing as android-4.2.1_r1.1 and android-4.2.1_r1.2.
The r1.1 file shows as being build JOP40F and the r1.2 file shows as being build JOP40G. The interesting part here, the JOP40G build was expected to arrive as Android 4.2.2. That aside though, to follow up on the remaining timeline, aside from the 4.2.1 version bump that arrived several months back, Google also released build JOP40E a little over two months back.
While these could be interpreted as minor bumps, there were some changes noted. The changes did not however address any of the Bluetooth issues. These are still expected to arrive as part of the Android 4.2.2 release -- whenever that makes its way into the AOSP. The folks at Android Police apparently spent some time digging through the code and noted the changes as being "very minor and mostly related to the Nexus 4."
Finally, for those who just happen to have an Android device and are wondering what an AOSP release means -- this is good news for developers as well as those who like to mod and hack. Basically, these releases mean it is not only possible, but also easy for you to get your device back to the original factory state.