Thanks for the addditional info.
A pack train trail is not a highway no matter how you stretch your imagination. My research has shown that many mining roads in Colorado were built by private mining companies with their own money and labor, on their own property. RS 2477 of course does not apply to such roads but the ATV lobby is trying to get access to private land.
The anti-landowner lobby would have you believe that RS 2477 is a good thing because it means no rancher or homeonwer can ever prosecute a trespasser. All the trespasser has to do is to say that he was on a RS 2477 right of way, and then the landowner has to prove that it's not. That's why RS 2477 is so popular with trespassers and ATV riders.