You could likely use a utility box knife to slice the insulation off the telephone cords.
That is if you're talking about the telephone cords that attach to your phone or DSL modem inside the house.
If you're talking about the black overhead telephone wire then that overhead telephone wire is made of steel. I believe it's just coated with copper.
But if it's the steel wire even with copper coating then it's worth nothing at scrap yards unless you're able to put it in with some appliances or something if your scrap metal yard takes steel wire.