Far in advance it’s difficult to say, they will advise on the flight selection page “possibility of wifi” only. I seem to get it on about 60% of my 737 trips.

i believe all a330s are international/domestic but the range of the satellites providing wifi is limited to within the domestic service area. Happy to be corrected on all of this though as not my specialty

In short, I don’t think you can rely on having access to wifi on qantas domestic