Presumably the new yard has sidings which will handle 1500m(/1800m?) trains, and how does this compare with the length of existing sidings?
If Beaudesaut Road is at a summit and the summit is lowered by 10m, how much fuel is saved per train lifting the load?
Roads should be in the vicinity of 1500m given they plan to shunt the terminal from the Sydney end. Currently, New Crane area and A-track can hold near enough 1500m long trains clear of the mainline but foul of other roads. 1500m in A-track does require the road set for the mainline to clear Kerry Road level crossing. Shunting won't work from the Sydney end if this isn't rectified.
Beaudesert Road isn't the top of the grade, it was between it and Leroyd Road. I think going by what can be seen as it stands, the top of the grade will be closer to Leroyd Road then it currently is.
Regards fuel, won't save enough to make any noticable difference assuming there is a saving not an increase. The grade maybe less, but throttle notch will most likely still be the same, or only one less, and having to pull the train further at low speed to clear the yard, the effect of the downgrade from the southern side of Leryod Rd in gathering momentum to reach track speed will be lost.