I get the point that you are highlighting that they are short of experienced drivers, and have to pay more, just like aviation. But this is the same all across the board, especially with trades and transportation. Drivers, mechanics even general laborers to load the things are in short supply across the scene. Part of the problem is the 'two speed' economy as they keep referring to where mining is sucking those after financial gains into mine-site work on good pay. Why would you work as a shop mechanic in the city on $30-$50k when you could go to the mine month on/off and earn $100k+. Same reason Perth transit was advertising for housewives to drive busses during the week part time. Now with the older workers leaving no one wants to do the local stuff.
The train driver strikes rolling in Sydney are a good indication of where it gets to eventually. The lib gov have now given up and gone to threats rather than appease the union which has them behind a giant 8 ball. Like pilots the drivers could just walk off the job and what would anyone do?