That's massive by the standards of modern democracy. Can you name any issue which more people have voted on? Far less people than that vote in most governments.
NB: The comparison may be confounded by local behavioural standards. Participation in this survey wasn't compulsory, but Australia has mandatory voting in most local and national elections. So there may be a prevailing culture of compliance. Nevertheless, a cursory review of the popular press suggests the turnout is substantially higher than that expected by most pundits.