If anyone is familiar with telco construction practices, maybe they can answer this one.
The local telco was installing a brand new overhead line from the central office near me a few months ago. I stopped by and asked one of the linemen what kind of cable they were stringing and he told me it was thousand pair, 26 gauge (why they are still using such old technology is a topic for another post). Later, I noticed that every few blocks, where they had to tie into an underground lateral, they would route the cable down a pole, into a splice cabinet and then back up the pole to continue on. When transitioning from the overhead line to the riser on the pole, they installed a splice box on the overhead line and then run a separate section of cable down the riser, through some conduit and into the cabinet. The downstream circuit goes back up the pole and into another overhead splice. As far as I can tell, all of the pairs are spliced and routed through the underground section. There are only two cables in and out of the overhead splices, so I assume that they aren't splitting a subset of the cable pairs out and running it to the cabinet.
My question is: Why can't the overhead cable be routed through the short sections of conduit and into the splice cabinet? It appears that the labor to make up each overhead splice is about a week for one person, which is not cheap. Its probably more expensive to make the overhead splices (working up a pole) than it is to work in a ground level cabinet (not a vault, just a pedestal style cabinet).