Whilst I disagree with recruiting pilots to fly these aircraft, whilst there are underutilised type rated pilots within the group, the idea that it could be "flown for free" is not entirely correct.
Once QF have no more leave left to assign in those ranks, and are paying pilots min guarantee to fly a divisor less than min guarantee, only then will it be "for free". QF are currently reducing a future cost from the liability side of the balance sheet by forcing pilots onto leave. It's the same reason that they have not, and in the forseeable future, will not be offering redundancies.