I don't think that they are used much anymore, if at all. Most rail routes now have fiber buried along them by telephone service providers and the railroads get to use their fiber as part of the deal. Sprint was actually formed as a joint venture between US Telecom and Southern Pacific Railroad.
I've seen a lot of the same condition of old signal wiring in Virginia, West Virginia and North Carolina as well. I wouldn't be surprised if the copper thieves start going after that next.
