Hahahahahaha Free you have to be joking no one does anything any more for free these days. The NRM got Allambi gratis (Free) and then had to spend over $25,000 to get it bought to Adelaide by truck and that was with mates rates and the truck had a back load as well. The NRM does not get handouts from Governments like a lot of you may assume, the larger percentage of the money walks in the front gate or spends money in the bookshop.
Also if the new rail proposal gets knocked on the head the Adelaide Metro themselves still might need to bring a railcar or railcars in for some group in the future. There have been a number of runs like this of a special run direct from Adelaide to the NRM and back again after the do at the NRM.
It is there at the moment actually the connection, so really it does not need anything done to it, only one train at a time would be able to go in or out, so rebuilding the junction might prove to be a bit more expensive than they thought, so they leave it like it is now. A railcar set now can go in and back out using the junction at the bridge. The only bit actually needing removing is the Rosewater loop part, but that now is simply just a single point removal job and not even on the mainline either. The Rosewater loop I think is planned to be a bikeway/ walkway type of thing.