if you watch and recycleing videos, there are people standing along the conveyor belt hand picking.
so, yes, that is done.
the typical one-stream recycling is to separate both types of metals.
a magnetic conveyor separates out one type. the eddy current separates the other.
plastic bags with paper receipts of course, (here in NJ anyway) are on a separate waste stream and collected at the food stores and not with any other rubbish.
once you have separated the metals, what is left is harder to separate and as you do separate them, it gets harder and harder.
plastic containers are easy to separate from glass containers, but the whole line typically goes over open screens to let any broken glass shards or bottle caps to fall out.
basically it is all brute force work. with the nature of plastics, about the only thing of value are the caps and milk containers. the clear bottles have some 7 or more layers of plastic.