FWIW:
In Qld, ambulance officers operating under the Qld Ambulance Service act (and police, and fire services) do NOT have carte blanche to break the road (or any other) law. The Strict Liability of an offence does not necessarily apply but the driver of an ambulance may be held to account for their actions.
Also, there is very little evidence that 'rushing' anywhere is of any actual benefit in reducing morbidity or mortality in severe illness or trauma. A study in USA demonstrated an average time difference of <42 seconds between a 'lights and sirens' run to a hospital vs a normal drive. It DID however show a much higher chance of injury to both ambulance personnel and other road users from the dangers inherent in emergency driving.
As far as Mercy Flights go, the criteria are pretty clear. There must be serious and immediate threat and no better alternative, plus regulations are going to be broken. In Oz these days with the high standard of ground ambulance services plus RFDS and emergency helicopters providing medical cover across most of the country a genuine mercy flight would be very unlikely.
I believe RFDS does occasionally declare a mercy flight for landings on unsurveyed public roads.