If this weather reached them (a fairly big if - the Araucaria angustifolia forests are 1,000km further north, though also at higher altitude), it is unlikely to have harmed them. Native vegetation is very rarely harmed, as a 100-year cold is nothing to the amount of time they have been there. A lot of the trees alive now would also have been alive for the previous cold snap, or two (or three or four!). A lot of introduced ornamental plants are likely to be affected though, as people keep trying to go for zone denial - trying to grow truly tropical species, when they should stick to subtropical.
Yes, unless newly migrated to an area or the local climate has changed since they arrived native stands may have come through thousands of years of regional weather variations.
