Hours of operation/curfew Sydney Airport (Australia)

I'd noticed aircraft landing into Sydney airport prior to end of the curfew at 06:00hrs and was wondering why this was possible. For those who may also be interested I found the following;

http://www.airservicesaustralia.com/...rmation/sydney

Apparently there is a 'shoulder' period for certain international aircraft arrivals meeting strict noise requirements.

Regards,
Gregg