I didn’t actually know they were building a new wharf on Somes, it’s great that the island is getting more infrastructure. And great they caught the ants, obviously.
I’m not sure specifically about these ones but looks like they are pretty widespread in NZ (though not found everywhere):
We know of Argentine ants in many parts of Auckland, Northland, Waikato, Bay of Plenty, Hawke’s Bay, Wellington, Nelson and Christchurch.
https://www.doc.govt.nz/nature/pests-and-threats/animal-pests/argentine-ants/
About 20 years ago there was an infestation of them in the Bay of Plenty, Tauranga city council was coming around deploying ant bait around people’s houses for free.
Pale green stuff dispensed from a caulking gun, seemed to do a good job.