Aidan if moving freight by rail was viable, Australia post would not run fleets of interstate trucks to carry their parcels.

Hasbeen, that's a non sequiter. Whether Australia Post utilises rail says very little about its viability or profitability.

Rail is constantly competing with road to carry freight. Sometimes they win contracts, sometimes they lose. But even if Australia Post decided to move their freight by rail whenever they could, they'd still need a fleet of interstate trucks, as there are many places Australia Post serves on the way that are nowhere near a rail freight terminal, and there are many journeys that are technically possible by rail but far more practical by road (such as Adelaide to Townsville).

There is a big difference between inter state & intra state Aiden. Look it up in the dictionary.

Rail Freight into Sydney from the nprth is at near maximum.
During the day they reduce the number of freight trains because of the
heavy commuter traffic from Newcastle and Central Coast.
They then release the build up of trains at Newcastle for overnight
run to Sydney Chullora in both directions.
These trains are usually about 60 plus by two 40ft containers each.
They come down from Newcastle all night until about 5am when the
commuters start again.
I seriously doubt if the M1 motorway could handle all that traffic
with one 40ft container per truck.

I think that most people have no idea how much freight goes by rail.
Certainly the real estate agents selling units along the rail line
pretend that they do not know.

Hasbeen,
So let me get this straight: not only are you blind to the enormous changes (mostly involving efficiency improvements) that have occurred in the rail industry in the last thirty years, but you also imagine that interstate trucks can't stop at intrastate depots on the way?

Even the regulations for trucks registered as Federal Interstate permit intrastate cargo to be carried as part of interstate journeys (though that's becoming moot as Federal Interstate registration's being phased out anyway).