|>>|| No. 95879
ABC coverage was available to stream on YouTube. You'll see the legend that is Antony Green talking through the numbers from time to time. He's like John Curtice but less academic and more techy.
A couple of years ago I met him and he described how it all works. The AEC decides in advance who the top two candidates are going to be. Ballots are counted at polling station, and they initially report the first preference totals and the two-candidate preference totals. If it turns out they guessed wrong or there's a closer run for second place than expected, then they stop reporting 2CP and just report out the full count, which takes longer as they need to wait for all the stations to count each round individually. They were waiting days for a result in 2016 because the AEC got a lot of their 2CP calls wrong, and so both sides were stuck in the 60s with a dozen full counts to do.
Green's evaluation of the UK going to AV was that we would need to be prepared to give up election night if we insisted on bringing all the ballot papers to count centres and only putting out numbers when complete rounds of counting were completed. He's able to make projections after a few hours only because numbers are available for individual locations.