Please refer to 52.245-1
to find requirement to notify the PA of a need for capital rehabilition.
. ...The Contractor shall disclose and report to the Property Administrator the need for replacement and/or capital rehabilitation.
It isn't clear how these units became accountable as Government property, or whether a disposal action under the original or any other closed contract over 20 years continues to transfer accountability. You may work with your Governent Property Administrator to clarify accountability to coordinate a request for rehabilitation or disposal.
The Government can abandon property as described in 52.245-1(k)
(k) Abandonment of Government property
...(3) The Government has no obligation to restore or rehabilitate the Contractor’s premises under any circumstances; however, if Government-furnished property is withdrawn or is unsuitable for the intended use, or if other Government property is substituted, then the equitable adjustment under paragraph (i)
of this clause may properly include restoration or rehabilitation costs.
The information in Paragraph 3 may provide your answer. More information is needed to understand if this property has an on-going requirement that justifies the provision of the units as Government Property in accordance with FAR 45.102
. Please don't hesitate to ask another question if this response isn't entirely satisfactory. Thank you.