I actually heard this years ago, just a few years after the ATSF collection was moved to Sacramento. I heard that it was not only the copper traction cabling, but some of the radiator sections as well. I surveyed the SP 4450 (SD-9 w/ boiler) at Golden Gate last year, copper thieves had hit it at some time.
I just got back from Brooklyn yard in Portland. Doyle has made great progress on his Alco PA. One of the bigger hurdles to completing it is the cost of new traction motor cables, the originals being salvaged by the railroad long ago.
With the price of most scrap metals continuing to climb due to worldwide demand, just imagine how much history will be lost or damaged.