So the thieves just lurk around the area, waiting for trains to come to a pause, and then break open the containers, I guess the containers are not very secure? And there's minimal patrols? It just seems like extraordinary 'easy pickings'.
With tamper-evident containers, you have a trusted person watch the container being loaded and locked, and then a trusted person watch as its unloaded at its final destination, and you don't have to care what happens at every point in between.