EFIS I dont think they grounded any RPT operators but with the CASA media release stating:
The Civil Aviation Safety Authority is working to ensure airlines are following the correct procedures when making decisions on flights while the volcanic ash clouds pass.
Two major RPT operators out of Adelaide may have interpreted it as : "If you fly and any of your aircraft sustain damage, we warned you and will have a field day with you."
It just seems funny that REX had no problems flying the week before but this week decided to pull the pin......Hindsight maybe.
On another note, i did hear a rumour one of the internationals that landed tuesday morning had signs of flight through ash.