I have seen his rig described in guitar mags, and not necessarily local ones - I found a page via Google that promised to link to another page that would reveal all, but the page wasn't there.
If that doesn't work, ring up Australian Guitar and tell them they HAVE TO DO AN ARTICLE ON JOHN BUTLER'S GUITAR RIG IMMEDIATELY!!!! And they'll tell you what issue they already did it in...
Luck - he's a great player but I don't like his toons much.