Keith
I think you are wrong.
The part time policy in the EBA simply states a defn of a part time pilot (employed ongoing but for less rostered duty time than a full time pilot).
No mention of pro-rata pay therefore if not negotiated it would have to be the base pay.
only pro- rata is for leave and redundancy
I would take that I will work 30, 50 60 hrs and get the base salary that is based on 75hrs.