most power lines are on a right-of-way,the land is not owned by the power company.There for making it private and it would be to the owner to say yes or no.
That's correct. If someone doesn't want you there, they could go after you for trespassing. I have a 60' power company ROW on my property and they have the legal right to access my property to maintain their towers. I can't build anything on the land nor block access, but I still own the land itself and anyone wanting to use it for ATV's, hunting, biking, etc., would have to ask permission or they would be trespassing the same as anyone else's property.