If any Australian speaker were so careless to use any a Australian colloquial terms he would be seriously spoken too - WTF, really?!
Although come to think of it, isn't informal Aussie speech sometimes peppered with swear words? When my dad went over as a ten pound pom, 'pommy bastard' was used as friendly banter/term of endearment as well as abuse, from what he told me.
Imagine two Aussie JW brothers, Shane, a pioneer, and Jim, talking in the KH. Shane tells Jim he's gotten all his hours in for a whole year.
"Shit a brick! Shane, you're a fucking legend!"
That would go over like a lead balloon.
I'd imagine they'd get a serious talking to.