I have only ever seen one which looked like in the Triad Movies but this was 10 + years ago and in San Po Kong (Not your typical Expat Area), across from my building is a small street which had 3-4 mahjong's parlors, i was bored looking down and suddenly saw 3-4 cars stop and a bunch of guys get out and rush inside one MJ parlor. Didn't actually see any fighting but it was mostly likely show of power or intimidation.
About 10 -15 mins later they all rushed back out and crossed the street to the other side and broke off into different directions.
That was the closest i have ever seen to a Triad Movie gang situation.