Bun snatching
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
http://news.yahoo.com/s/ap/20050502/ap_on_fe_st/tower_of_buns
I now believe every word of this film to be true.
Go Mak Dau!