There may be a difference in certain regions, but usually swarms are a spring thing, with another small reoccurrence in autumn. Mid summer is quiet and winter has none.
This relates to the times at which a queen can mate - there are no male drones in winter (the females kicked them out!) and so any queen that hatched would be a virgin, and couldn’t lay.
Sometimes swarms will occur due to bees absconding to get away from High levels of disease. I have never seen this but high levels of varroa can cause it.
NZ is lucky to have fairly easy going bees - this doesn’t mean that they are all friendly, just that Africanised bees are so much worse. There are accounts of them flying into smokers and putting them out. It’s all rather intense.
I think they still have the bees. Haven't heard much about it lately.