anchor: If there are economies of scale in delivery, and certainly if mail recipients do not want multiple carriers accessing their mail boxes, it would be possible to define routes, along with their expected workload, and auction them off to the lowest bidder.
positive: It would be possible to define routes, along with their expected workload if there are economies of scale in delivery.
negative: It would be impossible to define routes, along with their expected workload if there are economies of scale in delivery.