The Old 97's have not. In fact the closest thing there's been to live Old 97's on your side of the date line, is when Rhett did a solo tour of Japan after the release of The Instigator in 2002, where by all accounts he drew throngs of screaming Japanese girls, and included several 97's songs in his nightly setlists. In fact until recently - and maybe still - RhettMiller.com came in two language flavors, English and Japanese.
As for the Old 97's, outside of the U.S. and Canada, IIRC they've done just two overseas tours, both to Europe, the last one in 1997 in support of Too Far To Care.
Just out of curiosity, how did you manage to run across the Old 97's in Australia?
Cheers,
frank