On the NSW registry of 2004, there were about 100 pitbulls all up. So they're all unregistered - so not really pitbulls or there are very few around. Like every shark that chomps someone is a Great White. In fact wobbegongs (carpet sharks or aussie terriers of the underwater world) chomp more people than any other shark.
So if they don't know what it is, it's probably a bitsa. It might look like a pitbull but you're really going to have to judge on its merits. Is it trying to lick you to death - good dog. Is it trying to eat you, get out the sedative - bad dog.