Christmas in Australia is summertime so a lot of people have picnics in the park (ham, cold turkey / chicken, salads, etc) or a BBQ (seafood, salads, etc).
Lots of family groups also opt to go out for a Christmas lunch at a hotel or club so they can enjoy family time without having to do the cooking.
Churches and charities provide lunches for the homeless or those who are alone.
Christmas in our household is pretty much non-existent, just a casual lunch, no decorations / tree / exchange of gifts - our choice !