According to Jerry Sullivan, president of the local UAW chapter, the reason the company and the union are implementing the rule is to support their employer and to get people’s attention.
"Everybody's in this together," Sullivan said. "(We need) to buy the products we make and support the company. This is a good start."
The Dearborn Truck Factory is the only plant to enact the ban so far among Ford's facilities. Reaction from other union members and the public thus far has been mixed. Ford is not the only domestic automaker to implement such a policy: General Motors' Warren Technical Center has separate parking facilities for non-GM vehicles.
[Thanks, Jason, Wilson, etc. for the tip.]