They used to gripe about the excess cables under computer room floors and above T bar ceilings is always a nightmare.
I am not sure I have ever heard anyone say anything about cables in walls and the answer was always to simply label them "future use/spare". The problem is that most old wire is not suitable for modern communications. It does get down to the fact that only sloppy wiring can be pulled out without damaging the building finish. If it was diligently strapped, it is not coming out.
'Old cabling' above t bar ceilings is routinely removed from most interior renovations of comm spaces.
Anything that is 'to remain' is made as compliant to code as possible. Usually, this is cabling to adjacent tenant spaces, and most was previously installed without inspections. I refer to this as "sins of the past".
As Greg implied, the majority of the 'existing' is very rarely re-used.
Word of caution! I asked a contractor to remove the unused communications wiring and he said he would over the weekend and he did. Monday morning I came in to the phone ringing off the hook that the people in the floor above the floor that was being remodeled were fit to be tied because their phones and computer system were out. I was the bad buy.
You would think with the abundance of lawyers we have here in NJ, I can't believe one of them didn't write that article!
To expand what I said above, all the responsible property owners & managers have been cleaning up 'sins of the past' since I arrived in the town in 2001. It took a little conversation, but afterward, it's all considered 'part of the renovation'. I've heard of a few issues as to what George had, and that may be 'murphys law. I once (as EC) had a total gut demo job; five minutes into cutting out the V/D cabling, here comes the local Fire Dept!! Cut the Fire Alarm telco line, even though 'MA Bell' techs assured us 'all lines are dead'! If I remember....that was about $500 to restore the line. That was the days of the 'Phone Company'!!
BTW, a few sparkies reaped quite a few $$$ with the V/D cabling at the scrap yards!
It may be different now but our scrap yard didn't want most data cable because there was so little copper for the amount of insulation and aluminum. They had a big plywood board with the price for various cables and the ones they didn't want at all. IBM Type 1 was on the "don't want" list as was the big 360/370 interface cables, most coax and modem cables. Their favorite was bare, that is why they can't keep ground wires anywhere.
I suppose it depends on the type of wire. Something like bell wire or maybe even CAT 5 has a pretty good insulation to copper ratio but the kind you want out of a building the most is mostly insulation with a tiny amount of copper. A lot of this cable was not made with flame testing in mind either. When we actually started looking at the cables we were stringing around the computer rooms IBM quietly started replacing cables about as fast as they could. Some of our old cables were down right scary in a place that was handling environmental air like a raised floor.
Everyone cheated on 645 and as the computers shrunk, the raised floor areas started becoming class A office space but still shared AC with a lot of computer room area. Of course the cube rats discovered all of that "wasted storage space" under their desk and all manner of flammable materials ended up under there.