They (Speciality Metals) pay out on the PMs present, so they must get back that value somehow. Are the copper smelters just paying them for them?
Maybe, depending on how complex it would be. They may just assay them, pay you on assay, and put them into the copper they're shipping.
I'm curious though - the metals must be separated somehow, by someone. The bars go to a copper smelter - who uses the copper, but they must be removing the others somehow.
A primary copper smelter's business is to process many millions of pounds of copper ore. The ore they deal comes from all over the world. It contains the variety of metals in circuit boards plus a lot more. In their regular flow of material, they can handle anything that you can throw at them. They prepare your material and then sample and assay it. Then, they put the material in with everything else. Everything comes out in the wash. The material they get from refiners is a pittance compared with the ore they run.
A reason that the electronic materials are so compatible is that the resulting bars are always copper based, no matter what they started with. Most all refiners use gas furnaces. Iron and nickel are commonly in electronics scrap, but they won't melt directly in a gas furnace. To melt them, they add scrap copper to lower the melting point. Therefore, all the bars end us copper based - perfect for a copper smelter.
The smelters even pay the refiner for about 65% of the contained copper. Some things draw a penalty, however. If the nickel content is over 5%, a penalty is accrued.
The smelters pay a very high percentage for the precious metals - more than anyone else could pay. However, it takes 3 months for the smelter to settle. You can get advances, but you must pay interest on them.