I have seen this before where the 10 Tunnels 'appear' to be just west of Sydney rather than 'over' the Mountains descending into Lithgow.
They jumped about a fair bit rather than showing the run as it is.
I remember as a small boy going to Katoomba in the early 50's of them attaching the Pilot at Valley Heights and the train steaming away to tackle the incline a few hundred metres west of the platform and around the curve past the the Coal loader into Springwood a few minutes away.
The run to Falconbridge wasnt too bad but from there to Linden was a good pull and I believe in past years, Goods Trains had both a Pilot on the front that went through to Katoomba and a 'Banker' on the rear as far as Linden.
It was possibly this 'Banker' that caused the runaway from Linden one night pre WW2.
If they were looking for areas where Trains had problems on the grades, one place about 4 kms East of Mt Victoria under Mt Boyce (Soldiers Pinch) was notorious for Trains to loose traction on the UP Main during the late evening and it was common to see the then last track on the UP Main stay out for far longer than the section called for and this was when the 46 class Electrics were in their heyday.