I ran across a reference to gangs in Australia and a documentray titled "Bra Boys". (No, they aren't cross dressers.) I've never been to Australia and have had a somewhat idyllic view of the place but this film, narrated and bankrolled by Russell Crowe, sounds like it paints a whole different view. The story is about a group of young guys that banded together to survive on the streets of a herion-infested ghetto near Sidney. The Bra Boys turned to surfing as an outlet and policed the ghetto to get the herion out. The story mentions a fight between the Bra Boys and off duty police that ended up with 30 cops injured.
I haven't seen the film but intended to as it sounds interesting and provides a view of a side of a country that you don't hear about. Here's a link to an interview with Bra Boy and pro surfer, Koby Apperton, who sidestepped a jail term after a murder his brother, Jai, was acquitted of and his view of where he lives:

http://www.surfermag.com/features/onlineexclusives