I got turned on to this ad by a CNN article, where they interviewed some guy involved witht the production. Yes, the wheels were weighted, with some car part. Aside from the obvious exceptions (a couple of lumps of wood, perspex holding the speakers etc) everything used was a genuine Accord part.
It took them something like 640 takes over 4 days to get it just right, and the aesthetics of the movement were a big factor - they wanted a lot of grace where components were *just* triggering the next link (eg muffler - wouldn't have rolled any further) and not brute force.
Apparently one of the elements that gave them the most hassle was the very first cog - the human element of rolling it down the plank made it very difficult to get right.