Comparison between Arrium's Southern Iron operation and Atlas is largely futile.
Arrium's SI benefited from the proximity of third party rail infrastructure, the costs of which were shared with other users.
The SI operation only yields approx 3mtpa. If they had had to provide their own rail infrastructure it would never have gone ahead.
The Middleback Ranges mines producing approx 9mtpa benefit from access to short haul, long established, sunk cost narrow gauge rail infrastructure - which is owned by the company.
With the ever decreasing prices for iron ore, there are now rumours that even some of these operations are under threat.