There is no concrete info because Jetstar themselves dont know what they're doing.
"Modern Award contract" only offered because the "paid in NZ-live and work in Aus" cadet scheme got a bit embarrassing in the S. Inquiry.
They are living day to day in there and what one applicant gets told and posts here will be different to the next applicant.
There are no promises, there is nothing concrete, even a contract you do sign may be whipped out from under you ala the NZ cadets.
Get some very solid legal advice of your own before signing your name to anything Jetstar.