I'm familiar with using MusicBrainz for MP3s. Is there an equivalent program that exists for video files?
Doesn't look like it, there's a few unanswered forum posts scattered all over the place. My guess would be because of the size of the movie it's not possible to come up with an efficient signature to do a quick lookup on, which isn't the case with 3-4 minute songs.
It's probably going to be a manual process, but there's some other tools.
Have a look at some lists that talk about extending Media center extensions and other apps that might help your manual process work better, in terms of getting other supporting info.