Getting into Qantas used to be like winning the lottery, everyone's dream job, but things have changed a lot over the past 10 years, to an extent it's really just another airline here, as the "glory days" are gone.
Who would really leave a high paying f/o gig at another airline to take a back seat on a 787 on reduced pay with the possibility of a long wait for promotion
There have been some F/O's go from JQ to mainline in the past as well, plus Network this time around may generate some interest. It's probably just a corporate thing to advertise positions available within the group first before advertising them to the general public.
If you're referring to mainline not being able to attract interest from the wider pilot group, let me ask how many would leave a regional turboprop, or a charter company in a remote community to come to mainline? The mainstay of mainline recruitment in the past really hasn't been current jet F/O's. It's still higher paying than other cruise relief jobs and I would expect a flood of applications from regionals and GA (and probably a lot from overseas as well) when general external recruitment starts.