It wouldn't take long to rebuild a single track. After every mishap on the transcontinental line e.g. derailment, wash away, etc, the damaged section of line has usually been reinstated quickly.
Our big land mass is the enemy's headache. We could send gangers across the entire TAR line in wartime. Ballast, concrete sleepers, spare rails etc can be dumped across a few dot points as preparation. It would have been nice to have living quarters in place, but canvas tents would do.
Even though Tindal would be a prime target, Alice would be wiped off the map first, thanks to Pine Gap. If Spencer Junction remained in operation, freight would probably not venture north of Kulgera. We would have to round up our camel population and put some teams together .... again, but this time, in post-apocalyptic Mad Max Beyond Thunderdome fashion...
I just had a thought... does Australia have a strategic oil reserve? What would power our NR Locos in wartime...
.... Back to the camel train....