To recap, here are the ten projects that Marshall previously stated would be assessed as priority by Infrastructure SA:
1) Completion of the North-South road corridor through metropolitan Adelaide
2) A grain/minerals port on Eyre Peninsula to ensure the optimum location for this facility
3) The GlobeLink upgrade of major export infrastructure
4) An extension of tram services in the CBD
5) Completion of the Gawler Rail Electrification
6) An extension of the O’Bahn between Tea Tree Plaza Interchange (current terminus) and Golden Grove
7) Grade separations at major metropolitan area intersections to enable removal of level crossings – prioritising projects based on their capacity to reduce traffic congestion and boost productivity

9) Sealing the Strzelecki Track
10) An underground rail link in the CBD between the northern and southern train lines
Number 5 is presumably academic as it's fully funded and pretty much underway.
I would have thought Number 1 has already been assessed to an inch of its life in terms of economic benefits, although presumably the tunnel vs trench issue needs to be resolved.