I thought that after working for one year on Contract C the next year you still have to work the 20 days a month but then you are not gaurenteed the pay so I guess in the long run it will be cost effective for Qantas.
I don't think they will get rid of the contract B group because if it is quite they don't have to give them work anyway so it wouldn't cost Qantas anything. The only thing with this group is that they can choose to have their weekends off but I guess Qantas has contract C to cover this slack now.