Whatever the 'reason' given for the AWT's, I don't think it is possible to shift a meeting at the drop of the hat.
If there was a significant weather event making a turf track unviable, then yes, probably do-able with sufficient notice.
I have heard of English jump events being put off because of snow/ice, and then moved to an AWT for flat events for the jumpers. Not what they entered for, but at least, all in the same boat, and racing together, in the appropriate grades...i.e. 3 mile chasers together, and two-mile hurdlers together. So, still a competition. But that type of extreme weather is unlikely here.
Early in the season, Riccarton transferred a date to Ashburton, as the damage sustained by the Riccarton turf from the National meeting had not sufficiently repaired. But there was adequate notice in that case.
Reefton may come in and confirm, or otherwise, but there have been instances on the West Coast where races have been put off, and the shift to another track refused by TAB crew, even though only up the road. [ Not the same as the affected club refusing the offer for commercial/parochial reasons, that's another scenario.]