The gist of Communicator's earlier #4062 is that JORN in Australia publicly admits to 1,000 - 3,000 km for their OTHR system, implying that actual range may be rather wider.
In addition to security issues, the "cagyness" of the ADF about the range of the Jindalee system is due to the fact that the range varies depending on the atmospheric conditions which dictate the frequencies being used. Throughout the day/night, many different frequencies are used just like in normal HF communications - generally higher freqs in the middle of the day and low freqs in the middle of the night.