You may authorize or approve a residence transaction expense allowance when an employee is performing a permanent change of station in the interest of the Government and has signed a service agreement (other than a new appointee or an employee assigned under the Government Employees Training Act (5 U.S.C. 4109.); and

(a) The old and new official stations are located in the United States; or

(b) The employee has completed an agreed upon tour of duty overseas and is returning to the United States to an official station that is at least 50 miles away from the employees last official station in the United States; or

(c) When the employee has been permanently assigned to a temporary official station.