I did some digging, and it seems the default OpenALPR configuration I was using actually downscales all input to 720p before doing any further processing…so these results/times are at 720p.
Just to double-check, I changed it to accept 1080p input without resizing and re-ran it against the same video. I still only got 7 “valid” plates at 90%+ confidence, though the plates were slightly different. It missed some plates from the 720p processing, and caught “1LANE” (a bike lane sign) as a 90%+ confidence plate that exists in the VicRoads system, however, it missed incorrectly reading TUG700 as TDG700. You can see the raw results here.