OK, as promised, I quizzed the vet, who was most helpful. His response:

Antifreeze poisoning simply isn't an issue in New Zealand. He has never seen
a case. That's never. However, it is an issue in the UK, where he has also
practised, and where it is the leading cause of cat poisoning. It makes
sense that this is probably a climate issue - the UK is colder, people are
more likely to have antifreeze around and use it. The leading cause of cat
poisoning in New Zealand is paracetamol, given by ignorant owners. He has
referred me to the Vet Poisoning Information Service, a British
organisation, for more info, which I shall look up when I have more time.
But he also said poisoning is not the issue with cats that it is for dogs
simply because cats don't eat everything they encounter, and that if I check
out the VPIS, I will see that cat poisoning hardly rates.

Rat poison is also not an issue in New Zealand. There are two aspects to
this. 1. Cats won't eat rat poisons. 2. The older rat poisons started having
a secondary effect only at the level of about 5 rats - ie, cats would have
to eat 5 rats in a row before they started getting any ill effects, and
those effects would not be fatal at that level of consumption. Some of the
newer poisons being developed do have secondary effects at lower levels, but
New Zealand regulations keep those poisons out of the country.

He also commented that he was not impressed with the American method of
managing risks, ie keeping all cats indoors at all times.