Two things here - water and rail.In regards to a desalination...

Two things here - water and rail.

In regards to a desalination plant in upper Spencer Gulf ie Whyalla - I can't see this as being directly helpful to ADN as the GW project is on the other side of the peninsula and there is no pipeline from there to Poochera (Poochera's water coming by pipeline from the Todd Reservoir near Port Lincoln).

Rail upgrade may be helpful in the distant future. There is a rail siding at Poochera on a line that runs between Port Lincoln and Ceduna / Thevenard. Both of these towns have ports but are not container ports. There is a possibility that the uDFS may drop the need for exports to be in containers (as stated in the DFS). There is also the possibility that other products - ie HRM - won't require containers also. This could potentially bring Ceduna / Thevenard (about 100ks away) into play.
Interesting to note that ADN's new Chairlift prospect sits right next to that railway line and is probably only 60ks from Thevenard.