"The Aus Govt is quite happy to take the money and nothing else will be said about it. "
This comment states it all. If the government was serious about the noise issue then surely they would prohibit the movement by most aircraft within curfew. Emirates would just have to wait. By prohibit I mean that ATC clearances would not be given and therefore the aircraft could not move. What if a controller just said "No I cannot let you takeoff as I will be knowingly allowing you to break the law"?. What happens then?
Also, Emirates is not the only airline to pay a curfew fee.