There is a great episode, I think on Mighty Trains but not sure, that follows the 26 hour rail trip from Narvik into Sweden, down through Sweden and then back into Norway to Oslo. The focus of the trip was the highly lucrative fishing industry from around Narvik and the need to run it to Oslo for transhipment to the European market in a highly efficient manner.
The line runs through hundreds of tunnels and up some of the steepest grades in Europe and in this episode ran during the winter so the whole snow clearing and line maintenance was featured as was the functioning of the refrigeration systems needed. To say that it is very easy to interdict is a major understatement.