If I'm not mistaken from my reading of the license text, you are correct that there is a copyright involved. CC-BY-SA 3.0 is a contract by the creator of a work licensed therein, where the creator agrees to allow others to share the work and create derivatives given the terms of the license. The License Grant section of the license specifically states:
Subject to the terms and conditions of this License, Licensor hereby grants You a worldwide, royalty-free, non-exclusive, perpetual (for the duration of the applicable copyright) license to exercise the rights in the Work as stated below:
(followed by the things you're allowed to do with the work — distribute, remix, adapt, transform, etc.)
In other words, the existence of the copyright held by the creator of the work is what allows the creator to license the work under CC in the first place. I'll admit that they could probably have been a little clearer about the matter, since people can easily draw the same conclusion of "oh, c-with-a-circle-around-it = 'all rights reserved'", but to the best of my understanding, the creators of this film will hold the copyright to it and hold the copyright to any work product relating to it. They simply cannot use their rights as copyright holders in a way that is contradictory to CC-BY-SA 3.0.
Caveat: i'm a fucking education grad student, who the fuck decided i was qualified for this shit, i'm just reading what the license says