Hi Ollie
looks like a 787 license is NOT essential for that job. Remember, Jetstar already operate the 787 and I would guess that they would like the applicant to have the license so if they send the 787 to Auckland, they could sign off on a fix.
This doesn't support any rumour that 789's are going to Jetstar.
Plus, it's not setting up a maintenance base in AKL. The advertisment clearly states "line maintenance"