M I don't know what the Northern Coal loco fleet looks like these days but I suppose with the 92s and however many TTs up there now they may have less need for 82 classes . The 90s have to stay but it would be interesting to know if and how many 82s they could spare . Plainly the 4000+ horsepower ACs and 90s can do the job better than 3000 odd horsepower DCs so it makes sense to concentrate them there .
If they can spare some 82s they would obviously be able to replace 81s Gs Cs doing the same job but probably with less fuel dollars .
I'm beginning to think that AC loco performance and fuel costs are driving some of these aquisitions at times along with new contracts . Diesel fuel is only going to get more expensive over time so fewer units with higher tractive effort can pay off .
It may be interesting to speculate the load differences with ACs vs DCs and how it can equate to unit reductions and overall cost savings . I don't know the loads and conditions in the Hunter Valley but pics I see show 3 90s or TTs leading the bat wing trains and my guess is that 4 82s could possibly do the same job but it ties the extra unit up and probably uses more fuel .
On the Sydney Melbourne corridor its common to see 2 LDPs on QRs MB/BM trains and they are almost certainly doing better fuel wise than 3 NRs on PNs trains that require more tractive effort and or performance than 2 NRs can generate . It does remain to be seen how a C44ACi performs compared to an NR in more level terrotory and you'd think a bit more horsepower would allow you to run trailing units off line (load limit 1 notch) a bit more often than you can with NRs .
Tonights MB4 will be an interesting trial , provided nothing lays down , and it would be interesting to know its load and length . I think many eyes will be "tracking" that one overnight .