Around here FedEx ground is all contract drivers. They buy the vans and get paid by delivery. For FedEx and other companies it is a great way to shave expenses. Driver do get screwed in the process though as FedEx is always messing with them.
There is a slight difference in visibility. If a contract FedEx driver drives like a maniac, it reflects badly on FedEx and the contracting company can be easily identified. With white vans containing no identifying markings, the contracting company gets protection from that level of identification.
This bodes poorly for street safety.