There are some aspects that are not brought out in the story. (and wouldn't be in the context of the story)
As most people know NZ'ers may live and work in Australia without restriction, but since 2001 NZ'ers no longer have access to Australia's benefit system. All these arrivals will be post 2001 (obviously). NZ'ers can apply for Australian PR, under the same conditions as any other person, other than the fact that they can do it onshore and be in employment. The criteria is the same as any other person in the world though, and Australia is not an easy place to migrate to. The story talks about low skilled people, these folk will be unlikely to be able to get Australian PR.
But there are some other consequences. While there is such high employment in Australia, everything is fine, but is Australia ever goes through a recession there is a potential threefold whammy for NZ, since these migrants will probably return to NZ, as they are unable to claim benefits in Australia.
1 The unemployment figures in NZ as these people return to NZ (not forgetting if there is a recession in Australia, there will almost certainly be one in NZ) will increase disproportionally.
2 These returning citizens will be able to claim benefits in NZ, which will be a drain on the public purse. (I admit I do not know the criteria for claiming benefits though)
3 NZ will not have had the benefit of the taxes paid while been employed, as these will have been paid in Australia