Whilst CD1 (see https://www.youtube.com/watch?v=r7FipOh7NDA ) is for Robe Trains, CD2 is for Hamersley Iron trains. Prior to the connection between the HI and RR lines where they cross at Western Creek, all Hamersley trains went to Dampier. Robe owns the mine at West Angeles and was going to build a line there from Cape Lambert but when the Western Creek connection was built in around 2000, decided to buy 'Hamersley type' cars and use the existing line as far as possible. These days, most trains through CD2 are from Yandi.
The process is as follows; With around 20 cars left to tip, the next loaded train which has been waiting in the yard and probably already has a compressor-brake car attached, will move off towards CD2. As the loaded train approaches, the dumper will finish and a shunter will call the operator who is in Perth to ask for control of the dumper. The operator will withdraw the arm and give control to the shunter who cannot actually control the dumper, but simply lock it out. This prevents the operator from accidentally inserting the arm and/or moving the train or rolling the barrel over while shunting is taking place. As we go through the barrel, you'll see why that'd be bad. The hole is around 30 m deep and they once accidentally tipped a compressor-brake car over and because they're not meant to be tipped, they don't have anything for the grippers to grip so down the hole it went. Anyway, with the arm out, the dragging brake of the compressor-brake car holds the train in place. The shunter then radios the driver of the loaded train and tells him he can proceed through the dumper, pushing the empty train out as he does so. The loaded must hit the empty at no more than 2 km/h. That might not sound like much bit it's a 33,000 ton moving object hitting a 5,000 ton stationary object and the impact is quite significant. I prefer to hit it at 1 km/h but on occasions, myself and others have hit it quite a bit faster than that. While the loaded is pushing the empty for 60 m or so, the train has 484 cars (including the CBs), is 4,650m long, and weighs around 38,000 tons. If it's not the longest and heaviest shunting movement in the world, I don't know what is.
When the first car of the loaded is in place, the shunter gives the stop signal to the driver, drains the air from the train which applies the brakes to hold the train until the arm is inserted, uncouples the locos, and the driver pushes the empty 50 m or so with the dragging brake on the compressor-brake car still applied. He stops, connects the brake pipe, and cuts out the dragging brake (which is applied during dumping to stop the train running in and out with the constant stopping and starting and is the squealing you can hear all through this), checks for continuity, and then pushes the empty another 100 m or so over a set of points. While that's happening, the shunter unlocks the dumper, calls the operator and tells him to insert the arm and commence dumping. The operator will insert the arm and by remote control, activate the compressor-brake car meaning it'll put air into the train, releasing the brakes, while keeping its own brakes applied (the dragging brake) so as to hold the train while the positioner moves backwards to grab the next two cars while two are rolling over. Once in the 'tail track' (which is alongside CD1's tail track), the driver changes ends and drives the empty along the adjacent road where the CB car will be shunted onto the next loaded if it's arrived or into a siding if it hasn't. The train with then be set up for AutoHaul (or 'Robo Train' as I call it, see https://www.youtube.com/watch?v=BDbfDUqPm8E&t=115s ) and depart.
