So, as a railroader i have to say dont pick up anything around tracks because it is actually a felony but there aren't many railroad cops and just dont try to sell any of it as scrap ever. Also, there are a few points for consideration there. Yes, the scrap from refurbished is processed but you wont be able to buy it until its processed into stock so you wont save any there. Those big flat plates are called tie plates and they are tempered and the used ones make awesome striking anvils for lots of heavy work. If you happen to "acquire" some spikes and stuff its a great idea to show it off after you've moved the metal into a different shape but not before. Used rail is waaaay better for small anvils than new rail because of work hardening. Last but not least a lot of railroaders love seeing stuff made from spikes.
Hope this helps in some fashion!