I was working a downstream sector for that flight and can shed some light. As part of the sequenced arrivals system for Sydney, early arrivals (not curfew dispensated) are issued feeder fix times at around 4am local in an attempt to ease congestion at the 6am open doors at YSSY. Even though SIA221 is curfew dispensated, they were running late , were arriving post 6am and therefore caught up in the sequenquenced arrivals program. Their alotted slot time meant a 10min slow down from their estimate for the feeder fix. When issued with their fix time (somewhere over Leigh Creek) the crew stated they had a sick passenger & had organised an ambulance through company channels to meet them on their arrival and could they get some priority reference their ten minute slow down. This was their first mention of any sort of onboard medical issue to ATC. As they were part of the sequenced arrival program to jump the queue they needed to declare their MED1 status if the situation required it. If not the ambulance would still be there 10 minute delay or not. This is what the controller was trying to solicit from the crew. A declaration of MED1 status was all that was required but it was akin to pulling teeth and the frustrations of others on freq became too much for them to contain themselves.
The crew subsequently declared MED1, where given appropriate priority, tracked direct YSSY, the sequence was rejigged, other arrivals were delayed to make room and all was sweet with SIA221 arriving 15 min earlier than scheduled. The system worked. All that was required was for the captain to declare the MED1 status.
