George,
I believe Ashbys have stated publicly that they were not going to operate those NG locomotives at the Gorge because of the high rail dimensions and the potential for damage to the locomotives should they go down on the ties. I got the impression the locos might not ever touch the ties and this would be where the damage would come from.
Your points would probably be just more reasons not to operate that equipment there.
It was simply the rail height and potential damage that they commented on.
B.