The world of decryption keys in film world is interesting . DCP films have decryption keys that work in a time window. http://indiedcp.com/digital-ci... ... they don't actually control how many times the film can be run. This means 'super restricted' digital prints can still get played overnight - and they definitely are.
These nightvision things are to keep management happy - they have thick contracts with studios so 'security theater' in the theater has to be applied.
I was in a early screening movie that had studio security parading around watching people with the scopes after collecting cell phones and wanding people, it was redonk especially since the key was still unlocked overnight - and the movie had a rebellious theme but more physical security than any other.
To deter inside jobs there is definitely watermarking now, it's hard to spot but actually sometimes you can, may be a series of dots around a corner rather than some more carefully hidden signal. (and there may be audio watermarking too, but i think with two clean audio captures from different sites you could diff it out).