Two years ago I collaborated with a net-advertising company whom worked with some big industry names besides doing really cool motion-graphics and flash advertisement.
The music seems easily done when you see the whole reel (with sound effects and all) but trying to beatmatch (to keep tempos thus making programming reliable) different video slices with such different flows is a real pita. Thanks to some real cool tools in daws nowadays you can stretch or warp audio as you wish, keeping audio transients and musical motives on tempo with a streamlined non-matching video.
Also, at the very beginning you can hear an Oxygène-alike drumloop that was created in regular 4/4 measuring. If you pay attention you can hear it makes triplets between tonic measures, thanks to warping original regular quantization points to triplet (1/8T) quantization. You can do as you like without tempo nor measure restrictions.
The wonders of digital domain.