The Office of Personnel Management (OPM) issued its final rule for Phased Retirement on August 8, 2014.
The final rule states that agency implementation of this program is not mandatory; rather, implementation is discretionary for each agency. Agencies choosing to implement the program decide whether phased retirement will be available to all, some, or none of their employees.
The Postal Service™ has examined this program closely and has determined that it will not implement the program at this time.
— Compensation, Human Resources, 7-9-15