I've never made it that far through Headmasters, but now I must watch that episode.
+ In the opening credits of the Japanese version of Animated, Ironhide is in Sydney.
+ In the Cybertron TV series, Jetfire has an Australian accent... for some reason. For a similarly indiscernible reason, Power Bots Sideswipe has something that resembles an Aussie accent. As does Master Disaster from Animated.
+ Botcon Fallback speaks in Australianisms, (because he's meant to be Outback.)
+ Cover artist Trevor Hutchison is the only good thing from Australia to have any connection at all to IDW. Although Nick Roche has been to Australia.
(That's all I can think of so far.)