Originally Posted by ressu

I stand corrected. I took apart the cache.img. It contained a signed zip file (oddly, they have OTA updates inside the custom built tar system) which did replace quite a bit of files in the system partition (in addition to the normal CSC customizations). So yes, the CSC package does change more than the APN and default settings.

Sadly NPS will only work when a CSC is installed. Without it, you can't get updates through NPS.