In Settings → Cellular (Mobile in UK), settings can be changed regarding mobile data, including per-app switches for all installed apps to enable or disable mobile data.
Where are these preferences stored?
I've looked in /var/mobile/Library/Preferences, but there doesn't seem to be any preferences relating to this. I've searched through the plists for various strings including app names and IDs from the list of per-app settings, but not found anything.