Dale I have never encoutered this Aussie expression without the "flat out" part, viz "Mate, he was flat out like a lizard drinking." .. the irony or not is contextual and depends upon how it is used and in reference to whom .. it can mean both that he was just working very hard and fast or that it was unusual for him to be working very hard .. the earliest reference I have is >>>
1944: Jean Devanney, "By Tropic, Sea and Jungle.", 227: "The mother [kangaroo-rat]went one way and the young one another ... It ran straight, as flat out as a lizard drinking."
1951: Dal Stivens, "Jimmy Brockett.", 70: "The Wednesday of that week I was flat out like a lizard drinking when the phone rang."
1952: John Cleary, "The Sundowners.", 183: "You've been flat out like a lizard drinking, but this cove is right with you all the time."
1970: Max Harris, "Australian.", 10 Jan., 14: "Have you ever copped the way those girls serve the community at the Sydney Telephone Exchang? Flat out like lizards drinking, all day long."
(Ref: A Dictionary of Australian Colloquialisms. GA Wilkes.)
.. so Dale I hope that helps mate and continues your education of us wierd Collonials from Downunder .. so goodonyamate ..
WoZ of Aus 16/12/04
Reply from Wizard of Oz (Newcastle - Australia)