Firstly, full points to Qantas for their amazingly quick response to my email. I emailed late last night and by the time I'd got into the office this morning I had an email asking for additional information about my travel. I emailed it back and within 45 minutes had a call from the same agent. Incredible.
The agent said it would go on the booking date and because the booking date was December I will earn at the old/existing rates. I queried twice whether the change in ticket number mattered and she said no, it was the booking date and that was the information she had. The agent said she would let me know if anything changes and reminded me to keep my boarding passes. I would have preferred it in writing but I guess this will have to do.
Also, I note that the website refers to 
booking, not ticketing:
Bookings made prior to 27 March 2014
For members with a booking made prior to 27 March 2014 in a fare class impacted by these changes for travel on or after 1 July 2014, we will automatically credit your account within a month of flying with the Qantas Points that applied when you made your booking.