Big Chief,
I have also been offered a phone interview.
I was told by Jetstar to expect firstly a review of my hours, Total, Multi Command, Turbine and Night. I guess to check I have the minimum requirements. Followed by a review of employment history. I expect that this could include not only the factual historical questions like "After this where did you work?" but also questions like, "Why did you take this job?", "Why did you leave this job?", "What did you like or dislike about this job?"
I was then told that the interviewer would tell me about the recruitment to employment process
First hand information from friends who have successfully navigated the process indicate the phone interview is a relaxed interview but they do tend to ask one or more formal questions like, Why do you want to work for Jetstar and (forgive me because I cant remember exactly how it was described to me) but a behavioural type question to do with working with and communicating with different people like we do on a daily basis-Flight Deck, Ops, Terminal/Ramp, Ground Handling, Engineering, Cabin Crew Etc you get the idea.
As has been posted already it is a serious part of the process and is the first chance for you to prove you will fit in, so my advice is be prepared.
Hope this helps