Not sure why it needs to be an AU authority. Australia isn't exactly a bastion of research on COVID-19 for a few reasons: 1) we have limited research prowess to start with and much funding for research has been cut in the past few years, and 2) we don't have much COVID-19 to research (which of course is great but means we're not going to be the source of info on this).
Here's an article from just yesterday which mentions face masks reduce the risk of transmission by 50%:
Face Masks at Home Reduce COVID-19 Risk, Study Says
The study is talking about "at home" but you could extrapolate that to mean any closed area where people are together.