Those almost look like the arches the DT&I had when Henry Ford wanted to electrify. I remember due to high cost, he didn't have them removed
It was partially due to cost, but also the fact that being that there are so many it would mean full closure of the tracks for months to remove them all. They'd started removing them a while back. To their surprise they found that they were very hard to remove so they decided to leave as many up as possible since they've survived this long they knew it was safe to leave them up. They just went through and found the handful that were in danger of collapsing and removed them.
I've read that they're just gonna maintain where they can and the remove the ones that will fall apart.