KELPIE
I think you are getting your airlines a little mixed up.
Jetstar is an Australian airline flying VH registered aircraft with some Singapore and Thai based crew working for them and they do not ever operate on the Singaporean registered aircraft.
Jetstar Asia is a Singapore based airline flying 9V registered aircraft with their own Singapore based cabin crew that do not ever operate on the Australian registered aircraft.
It is a requirement for all Australia crew to hold this certificate when they commence flying. I am aware of many flights leaving Australia with only Singapore crew, which means that no one on board was trained for any medical emergency.
So really the question is, Which airlines cabin crew are you talking about ?