Jimmy I think we are all in agreement that it is a Strata Building insurance claim and the only difference is who pays the excess.
If it was common property I would agree that in NSW it is Strata reasponsibility to cover the excess but it is not common property the fixture belongs to the lot and so it is the owners problem to pick up the excess.
This is one of the confuseing things about strata insurance it cover both lot property and common property. If the item was damaged by a non insurable claim would you expect the Strata to pick up the bill for the total repair of a clearly lot item.
Whether the damage was caused by strata negligence or origional builder negligence opens up a whole new bag of worms which I am not even going to try and argue for or against.