Evidently you don't remember what an execrable mess the railways were under state ownership.
I think you missed the sarcasm. Railtrack/Network Rail is an omnishambles whichever way you look at it.
Anyway, let's not forget why the railways were nationalised in the first place (they were bankrupt) and that the privatised rail companies have trousered more in subsidies than British Rail did.
FWIW I'm not a fan of Corbyn at all but I don't think that has anything to do with this.