There is an easy process for providing proxy services, the real data just needs to be sent to a third party, its the process used with ICANN so wouldn't be that difficult to do the same sort of process, even if Ausregistry have both sets of data with them in the case a registrar goes out of business or is no longer accredited.
Although .au WHOIS doesn't show that much data to begin with so sort of useless in my opinion.