Expanding on @jlovegren's comment:
It turns out there are similar idioms in American, Indian, South African and New Zealand English.
This concept has popular culture references in How I Met Your Mother and Punch Drunk Love.
There is a study on this by the University of Pennsylvania.
In the Australian case - there is a study:
[K. Burridge and M. Florey, "''Yeah-no He's a Good Kid': A Discourse Analysis of Yeah-no in Australian English", Australian Journal of Linguistics, 22(2): 124-171, 2002. Here's the abstract:
Yeah-no in Australian English is a relatively new marker which serves a number of functions, including discourse cohesion, the pragmatic functions of hedging and face-saving, and assent and dissent.
Also on the Australian side, there is this article in the Age.
So in conclusion, there seem to be similar phrases across dialects of English, but not with necessarily the same meaning. (One might add, their meaning seems sufficiently context-specific and flexible that there are few established rules on this. )