This is of course big business as the price of metal can very hugely due to demand. But it's fair to say there are different types of metals on different vehicles, from steel to aluminium and certain alloys and these do need a slightly different process to re-cycle.
The Crushing Affect
So when a vehicle is crushed, items such as alloy wheels ad engines will first be removed and if not re-sold to improve the looks or prolong the life of others, these will be kept separate.
At the melting centre, the different metals will be dealt with appropriately and will re-appear as different products, such as tins for your beans, washing machines or even to be used as panels in another new vehicle.