It's hard to explain. All the songs and motifs are imports save for a few local ones, but most of the practical acts of the holiday are a mix of traditional stuff with a southern flair. BBQs are as popular if not more so than traditional roasts, and in our family, we cook the ham and chook early and have them cold for lunch. There's a lot of beach happenings too.
Tbh though, the most important and sacred holiday event to a good proportion of the population is this https://en.wikipedia.org/wiki/Boxing_Day_Test