They pick those up with a crane with an electromagnet and load them up to head to the scrap yard. Might be a better idea to sneak a few from somewhere else where no one is a lookin.
Not much goes for scrap-especially tie plates.A lot of them are obtained from track upgrades to heavier steel-the salvaged plates and other material is re-used when laying track spurs and sidings.some badly curve worn or damaged rails are sold for scrap,but lots are re - layed in lower classed track.
Even old bent spikes are straightened and re used,unless throat cut.