Sudoxe:I am agnostic as to how urea is transported. I like...

Sudoxe:
I am agnostic as to how urea is transported. I like trains. I've spent a lot of time around them.
Here is a simple formula to approximate your transport costs on the Leigh Creek Railway [Leigh Creek Open Cut to Stirling North Junction] :
LCK costs for urea transport [$ per tonne] = Rehabilitation Costs + Historic Flinders Power costs for coal transport [$ per tonne] X 2.7 X inflation % annually since 2016.
Assumptions : No SA Govt assistance. The SA Govt is notoriously stingy when it comes to supporting railways, except for the suburban passenger system. It refuses to pay $330,000 pa to support The Overland train from ADL-MEL. Perhaps they might suddenly develop a socialist bent and transfer some costs from you to the SA taxpayer. Seems unlikely.
No other large scale user turns up to share the cost. I know nothing about the magnesite people. The guy who delivers the camel meat for the burgers at the Parachilna Hotel says he can't wait for you to get up, so he's going to take it up in the van.
Flinders Power transported about 2.7 million tonnes of coal annually. LCKE only 1 million tonnes. So the infrastructure maintenance cost, when exressed as $ per tonne will be 2.7 times higher.
Once you get out onto the DIRN the cost structure changes. I have no idea how far you are planning on sending your urea, not to Adelaide I have been told But the further you send it, the longer it will take for the locos and wagons to come back.