There really is no need for secrecy, these trackers are well known.
There are various versions of live tracking in Australia. I may get some of the details wrong, so I'm happy to be corrected.
Let's start at the top. The main live tracker for Australia is called 4trak, I believe it uses a mix of gps and cellular data to monitor train location, speed etc. 4trak manage this data and display it for their clients, such as ARTC and John Holland amongst others.
It is private, with no public access available. That being said there seem to be quite a few who do have access. Some people are very good at discretely sharing 'sightings' from the tracker, most seem to keep it to themselves and their buddies.
There was a tracker built into Railpage that used the 4trak data up until 2017 when public access was stopped. There was also another public tracker using the same data from 4trak but that was also affected by the 2017 shutout.
Each company also has it's own fleet tracking. I know Pacific National and SCT have one, and again there are people with access to it but they seem to keep it for themselves and their buddies.
In terms of what is publically available right at the monent for freight tracking, there is anytrip.com.au on which you can see freight most in the Sydney suburban area, and as far north as Wyong (I think), as far west as Lithgow, and as far South as Campbelltown and as far on the south coast as Helensburgh.