USPS Closing Contract Postal Unit

According to a note on the National Association of Postmasters, US (NAPUS) website, the Postal Service is closing 20 contract units that offer virtually the same services as a Post Office. (i.e. Retail, PO Boxes, etc.)   The note implied that the closures are related to the APWU agreement. These closures raise questions about what the Postal Service's retail strategy is and how labor and contract unit contracts affect that strategy.