You could probably run a robot along the high voltage lines (birds sit on them all the time), but I imagine the main problem is jumping from segment to segment

You could probably run a robot along the high voltage lines (birds sit on them all the time), but I imagine the main problem is jumping from segment to segment when you reach a pole (partially because you might accidentally ground the robot, but mostly because acrobatics are hard, especially if you're tangled up in tree limbs, etc).