Bicycle definitely wouldn't fit in a 5-gallon bucket (or a 20-gallon one, either), but it does travel from cache to cache... It has a chain with a lock; cachers leave the bike chained up somewhere in the vicinity of the cache and leave the key to the lock inside the cache. (They ride the bike away after retrieving it.)
Looks like a fun and creative TB to me.
Oh, I really hope bicycle makes it out here to Oregon - we would have loads of fun with that TB!!!