The way the trees glow white in the plane view at 1:09 -- could they be using near infrared cameras or filters to help specifically with tree detection? Nowhere in the color video do the leaves look that bright. The paper doesn't seem to mention it though.
It definitely looks like infrared to me. The paper mentions that they use a pair of Point Grey Firefly MV cameras, and the reference manual for those cameras[1] says that "in monochrome models, the IR filter is replaced with a transparent piece of glass."
http://groups.csail.mit.edu/robotics-center/public_papers/Ba...