I'll throw my tu'pence worth in... The containers in the video were leased from 'Amficon' in the early '90s and used primarily for grain, and also for a short while Tara to Arklow. This came about as Tara mines were unhappy with the fees being charged by Dublin port. Flow only lasted a couple of months. On the previous site I asked if Arklow ever had a Container crane in the yard (it didn't) so it was forklift and transfer by road to the port of Arklow.
Re unloading of Beet wagons: I've seen a video in the past somewhere of the Mallow sugar factory, and the wagons being unloaded. It was always done at night as all the road traffic was dealt with during the day. Think there were 3 of 4 sidings inside the plant, so they could turn the trains around very quickly. And basically a giant high pressure water jet on a hydraulic arm was lowered into the wagon and the water blasted the beets out of the doors of the 2-axled wagons, while also cleaning the beets! Simple! This also explains why the 40' beet containers had the side door located on the ends as opposed to the middle. Easier to push the beet out in one direction.
Finally, thanks for answering a question I had in the back of my head re: 20' open containers painted in blue. CIE/IR had quite a number of these containers (with crudely-cut roof openings) and I couldn't figure out why some were painted blue, when most were brown as used on the coal trains.
Take a look at Eiretrains, and especially stations on the Western corridor as there are plenty of pictures of the 'coal n oil' and you will see the odd blue container mixed in to through the rake!