Update:
I have not yet spoken to the neighbors since I created the thread, but I did message them asking if we could get together soon to chat - No response. Pretty clear they won't fully cooperate, but still going to approach them when I do see them out. They may be out of town too
But I did speak to my contractor who said that's great the county is onboard, but he wants them to put it in writing in case things get ugly with neighbors. So I reached back out to my contact with the county who gave me verbal permission last week to bring fill using the access way. Now all of a sudden, he is being more difficult and wants to complete a site visit to see if I can use this trail for hauling fill.
If somehow I get through this latest hoop, my contractor also wants me to get a survey of the county access way to ensure we don't encroach on anyone else's property (which I can understand).
Long ways to go, but the cards seem stacked against me. I can't believe how difficult it is just to bring some dirt to my property. Meanwhile, the county is plowing down thousands of untouched acres nearby for housing. I guess it is all about who know like anything else.
If this doesn't work out, I'll just bring all the dirt through the front of my yard. Will takes 2 weeks compared to 2 days...