Read the article and laughed when I came to New Zealand.
If that ever happened, a union between Australia and New Zealand, the small number of New Zealanders who supported it would be considered traitors. I can definately see some kind of violent conflict rising in the midst of a union there, and in the muck of it all, the various extremist groups would probably take their chances and stage multiple coups against the parliamentary democracy we already have as well as each other. The New Zealand National Front would most definately try something, as they are already trying to set up an independent nation within New Zealand that is free of anyone except Christian whites (or whites in general, tbh I couldn't care less about the NZNF). The smaller groups like the New Zealand communists and all that would probably wriggle up in some way as well.
All in all I can see this event being catastrophic for New Zealand. As for Australia, they would probably welcome the flow of new people to they can oppress. New Zealanders would probably become the ethnic minority within the Greater Australia, as the Aborigines have been and still are in many places, except maybe to a lesser extreme. The thing is, Australia would end up being somewhat of a Pacific Yugoslavia, especially if they absorbed Timor L'Este and New Guinea as well. Eventually it would be forced into dissolution, depending on the POD. This whole post is assuming this happens recently, i.e. tomorrow or the next day, etc. Way back when, when we were all "British", such a union (such as the New South Wales-New Zealdand union) wouldn't have been met with so much resistance. I know a couple of Australians who actually think New Zealand is Australian and were surprised when they came to visit that they had to come into a massive international terminal and go through major customs and all that. These same Australians think that Tasmania is a separate country, and that Australia is a republic.
I think it would be a shotgun wedding, if NZ and Oz got married. With Oz's daddy holding the shotgun and NZ wanting to commit suicide soon after.