Based on my (admittedly narrow) look at some of the records from my Great Uncle's 9th AF unit, gun camera film was often submitted to Victory Boards in support of claims. I have read, however, that 9th AF Victory Boards were notoriously stingy about confirming claims, perhaps because footage showing extensive damage didn't also show the final fate of the E/A.
If the issue, however, is whether that footage survives for researchers to verify today, I don't know whether the original films or copies were archived after the war. I know my Great Uncle brought home extensive reels of combat film, but they were lost in a post-war flood. Other members of his unit retained their combat film as well, because clips (both ground attack and air-to-air) appear on the 368th Fighter Group website (
www.368thfightergroup.com).