That is a fair point, and there is a risk that volumes are not sufficient to run more than one operator. Though with now 4.7mt on the route, im not sure if it is a high or low risk?And this I believe is one of the problems with the network in the central of Australia. There needs to be the ability for smaller or more aggressive operators to get access to network for service delivery. The same could be said for the many lines GWA have which do not carry traffic.
If you want to grow the central australian business then you need competition against road on the rail network. You also need a track owner who can build branch lines and industrial to service longer term projects in the way BHP/FMG/RIO etc do. Rail would be even more competitive.
You've got to be careful with what exactly more operators will actually acheive.
The Northern Territory is not a large market, the economy is only one fifth of the size of North Queensland's and the NT population is the same as the Cairns regional population - at 244,000. In 2009 GWA had acheived 90% market share on the Adelaide to Darwin corridor, handling 800,000-tonnes of intermodal and 71,000-tonnes of bulk liquids, and doing so at ten to twenty percent less than the cost road. In 2017 tonnages were at 4.7-million tonnes.
So additional operators will not be taking traffic off road, they'll be cutting into GWA's profit pie - which isn't huge, and all that for the sake of a perceived lack of competition. The Sturt Highway already represents competition for any disatisfied customers, and even more so, so does the Barkly/Landsborough/Warrego Corridor, which offers a far shorter transport route from the East Coast.
But what if a lower freight rail rate leads to more work being possible? Not that i think there is this case in the corridor (but I don't know there isnt either), but hypothetical lowering of freight rates might lead to entirely new business. And what might freight rates do to goods brought into Darwin/NT from the south in terms of their overall price - again if the overall price of goods is lowered, what might that mean for the NT economy? This is very much an academic question, and the transport cost might make a small portion of total cost of goods and so it could be irrelevant.
Overall though, the monopolist position that GWA holds there just doesn't feel right to me.
Ill make a new thread about this for discussion but the SA ESC is reviewing the arrangement as per its regular review schedule. Always an interesting read, especially the submissions from industry.