There certainly was at least one aircraft on the Australian register that was approved to use the Garmin 100 for IFR opps. CASA issued a special approval of which I personaly have not heard of before or after but the C209 (otherwise known as the C207-900) had "approval without restriction" to use the Garmin 100. Those if you not familiar with the C209 there is some very informative and factual information to be found here
http://www.pprune.org/forums/d-g-gen...-poh-hire.html
I cant put my hand right on a copy of the approval, not sure if I still have a copy or not........
Anyway last I heard when some operators from Kakadu and the Kimberlies approached CASA about bringing a few back into the country CASA said they would be unlikely to re-approve the Garmin 100 for IFR opps, kinda sad really.