You're probably already aware, but if not: Magic Lantern alternative firmware for the 5D makes it much much nicer for making videos. In the right hands (which are not mine ...) I've seen it make low-light video results much, much better.
Haven't tried it yet, unfortunately. Not being your own DP has some disadvantages too...
If you've seen any low-light footage with with manageable noise on it (forget manageable, just make it pretty) shot with Magic Lantern, I'd love to know about it.
This movie is from Trammell Hudson, the guy who created Magic Lantern. He doesn't mention that Magic Lantern had anything to do with the low light performance, so I assume the performance is plain 5DII - however, features from Magic Lantern can help you get the focus, exposure etc much better than stock firmware. (I am sure, however, he used ML when taking this video)
