You're right. I forgot about the decomissioned pipelines. Although,
you'd be surprised how stupid some of these morons with backhoes are! I
remember a major MCI cut along their west coast route a few years ago
that took out the entire northwest for 8 hours. The guy was 600 yards
away from where his permit allowed him to dig. He stopped when he cut
the fiber and shut his hoe down. When they got out there, they found
that he was digging right next to train tracks, was inches from cutting
a high voltage power line that surely would have killed him, and was
also fairly close to a gas line.
It's not always the equipment operator. I was witness to a ConTel fiber
cut along Route 66 aboard MCLB Barstow. The fiber was cut by, get this,
a road grader. The fiber was buried (if you could call it that) along
the shoulder of the road (which sloped upward about three feet), three
feet from the edge of the road, _at road level_! It was also over 6 feet
out of alignment with the orange markers.
In the process of widening the road, the grader caught the conduit and
broke it, along with the fiber. The operator didn't even know he did
it until the ConTel crew showed up.
Crude ASCII art of where the fiber was buried (in profile):