Readily available from home - Sky via Foxtel which is almost exactly 5 seconds behind live. Sky at a TAB venue via the commercial feed is about 4 seconds behind live.
Have done some rudimentary calculations (albeit I'm pretty confident in them) based on price movements at the end of races. Allowing for reaction time etc, someone has a feed around 0.5-0.7 seconds behind live (obscure country tracks add another 0.1 to 0.2 seconds as they are delivered by satellite most times). Tracksiders are present at some tracks, but it's happening at literally every track now including those with covid restrictions and tracks that are in the middle of nowhere and have 1 meeting a year so the bulk of it is the fast feed player/s.
The only protocols that allow for such low latency are direct terrestrial IPTV feeds and first hop satellite feeds, it's clearly Tabcorp. I think you've made a wise choice pulling your bots from AU in-play markets, I've all but retired from them too. This will ultimately kill our in-play markets, there has already been a significant drop in liquidity and I can't see that ever being turned around now.
The cynical part of me wonders whether BF finally being granted access to a faster feed was contingent on allowing Tabcorp to trade on BF. I can't imagine that being the case but the timelines match up.