It's casual so you only get paid by the hour. So the rate is $20 per hour, and you get a flying allowance of $10 per hour (when you're in the air), you also get $60 per day if you're on call.
There are rumours that the casual positions could lead to full time but a lot of those rumours have been shut down by "people in the know".
I don't know how "ruthless" they are ... I got through and am starting GS for SEQ next week. But I've been trying to get into the industry for 2 years. I don't know how many other people got through, but I think we calculated that about 300 people were at the initial RD's.