Rumour has it that the Southern Australian introduction of the BAe146 ran over budget to the order of 100%. Kendall's jet introduction was far more costly than expected with much longer training times than expected.
This doesn't mean that Eastern or Sunnie's pilots can't fly jets, but it does indicate that for a large fleet replacement and retraining program, the costs are very high. It's hard to understand why QF would expose itself to such costs.
Train a whole lot of people to fly the Dashes, to release the existing Dash pilots to get endorsed on the A319. Perhaps direct entry commands for both. Plus the possibility of contract pilots for some period, to massage the introduction. A whole lot of room just there for industrial unease, I'd think.