J/D awards on these non-stop transcons would go early because much of this seating would go to folks continuing on to SYD or Asia. As well, some capacity is assigned to C for upgrades. So you are likeliest to get J/D seats with a connection in YEG or YYC. You could book one of these, then at the airport try and standby for a non-stop.

Otherwise, if you need the miles, and hold elite status, buy a cheap ticket on the flights you prefer, and if they also happen to be full/overbooked, you stand a good chance to be op upgraded.