It probably was prearranged, yes, but he did a good job of showing how it works. Notice how once he polished the aluminum can he just set it in place and left it there to work. It looked like it wasn't until some time later that he noticed smoke coming from the tinder bundle. I appreciated seeing Les light a fire in this manner because, since I first saw this on MythBusters, I have never thought of just leaving the can-mirror in place instead of holding and focusing it.