Apparently the bun-snatching sport featured in the film is real. And the practice really did come to an end when a tower collapsed, injuring competitors. An AP article from 1 May 2005 describes the resurrection of the activity on Cheung Chau island:
Bun Tower Climbing Returns to Hong Kong
by Min Lee, Associated Press Writer
I now believe every word of this film to be true.
Go Mak Dau!