The mass recruitment of MAM casuals in shorthaul is in preparation for the end of the current shorthaul EBA. I have it on very good authority that the company is looking at removing band payments for shorthaul crew for the next EBA.
As for the 747-300’s. There are only now 4 left operating as VH-EBT is now out of hours and is being scraped or sold. They will also only be operating domestic sectors (unless used for disruptions) for the remainder of there service life.