CBH (Cooperative Bulk Handling) a grower controlled organisation operates the grain trains in Western Australia. They currently have 25 Motive Power (Boise) CM27C and CM33C Locomotives, all CM27C units on narrow (3’6") gauge and CM 33C units on both gauges. They currently have 572 grain hoppers on both gauges.
CBH have decided upon a dramatic expansion and are purchasing 7 new standard gauge locomotives and have just announced an order with Wabtec for 17 new locomotives from Wabtec. They are also buying 200 SG grain hoppers and 450 NG hoppers from CRRC China. This pretty much doubles the fleet size.
These are not a continuation of the Cummins engined MP series but are model CM20ACi units with 7FDL-8 engines. They are also AC traction. It is expected that these will be externally similar to the CM20EMP type provided to Indonesia as type CC206, but are of course AC traction rather than DC.
The last GE USA locomotives built new for narrow gauge in Australia were ten 1200HP units built for Queensland with FVBL-12 engines in November 1952.
The new units will be less powerful and lighter than the existing MP27C units, although with AC traction they may be able to haul the same loads. This might not be a big disadvantage. While stopped in the terminal station of Miling on a wet day, an MP27C managed to fall onto its side on the unballasted track. It was revered easily and quickly but the track repairs probably took longer.
Interestingly, the standard gauge locomotives were ordered from Progress, possibly because Wabtec don’t have an existing design for Australian conditions.
Railfan son in law in Sydney has 2 views of the narrow guage arguments. He does like NG preservation movement but cannot understand desires to have NG main line interconnections or worse the use of dual guage tracks.
IMO changing out NG sleepers a major problem but start now just replacing worn out sleeepers with longer ones. Concrete ties made for both guages. There is the question would sleepers ends need ballast underneath to prevent breakage? That could be a major expense.
EDIT: What are the standard Australian sleeper lengths for each of the guages?
I probably should have further explained the use of two gauges in Western Australia. Firstly, Western Australia is big. It is around the size of the Western 1/3 of the Continental United States, but has smaller mountains but possibly bigger deserts.
Here is a map of the southern half of Western Australia showing the railway gauges:
I’m viewing this on a 24" monitor and the lettering is still a bit small. Also remember that the Pilbara standard gauge iron ore lines have an extensive network, all of which is north of, and hundreds of miles from the network on this map.
I also attach a documentary about Western Australia from the 1950s. Apart from the standard gauge line to Kalgoorlie in the east of the state, the trains shown are all narrow gauge and all steam. They don’t still mine blue asbestos, and the name of the town has been removed from the map to stop people trying to visit.
The most recent locomotive design with two cabs from GE or Wabtec is the CM20EMP. I would expect that the CM20ACi would use much of the CM20EMP design with the AC equipment substituted for the DC gear. The cabs and hood could be taller but GE tended to use standard bodywork on their export units regardless of the available loading gauge.
This video shows trains around Geraldton in 2017. I was there at the time and met John Phillips while he was taking these videos.
Sadly the video doesn’t clearly show any of the sections using dual gauge sleepers (ties) mentioned earlier. It does show the heavy iron ore trains and the condition of the track generally. There are good shots of a current CBH grain train, hauled by two of the MP27C locomotives. These are the two tone blue locomotives, easily recognised.