ECU's yes, but basically anything. Anybody should be able to go to a breakers, buy a part for their car (obviously same model, same part number) plug it in and it should work. Why not?
This is not possible in a lot of cases and I find it difficult to believe that techs can't see where this could be going. I think the manufactures are aiming at a total block on fitting parts unless the vehicle ends up at the main dealers.