As long as the aircraft is receipt of a taxi clearance before 11pm local, the aircraft can depart 16R from the full length at any time.
Just to be clear, there was no dispensation required or requested. The Atlas 747 did the exact same thing last night. They had a taxi clearance at 10:59:45pm.
Whilst is was unusual to have 5 waiting to go well after midnight, the total delay for most of these aircraft was only 3 hours or so as they usually depart reasonably close to curfew.
http://www.airservicesaustralia.com/...SYNA03-110.pdf
Read: 4.4 (b) (iv)