The area of operation of a regional housing authority shall be decreased from time to time to exclude one or more counties from such area if the board of supervisors of each of the counties in such area and the commissioners of the regional housing authority each adopt a resolution declaring that there is a need for excluding such county or counties from such area; provided that no action may be taken pursuant to this section if the regional housing authority has outstanding any bonds, notes or other evidences of indebtedness, unless first, all holders of such evidences of indebtedness consent in writing to such action; and provided further that if such action decreases the area of operation of the regional housing authority to only one county, such authority shall thereupon constitute and become a housing authority for such county, in the same manner as though such authority were created by and authorized to transact business and exercise its powers pursuant to § 36-4, and the commissioners of such authority shall be thereupon appointed as provided for the appointment of commissioners of a housing authority created for a county. The board of supervisors of each of the counties in the area of operation of the regional housing authority and the commissioners of the regional housing authority shall adopt a resolution declaring that there is a need for excluding a county or counties from such area if: (a) each such board of supervisors of the counties to remain in the area of operation of the regional housing authority and the commissioners of the regional housing authority find that (because of facts arising or determined subsequent to the time when such area first included the county or counties to be excluded) the regional housing authority would be a more efficient or economical administrative unit to carry out the purposes of this Housing Authorities Law if such county or counties were excluded from such area, and (b) the board of supervisors of each such county or counties to be excluded and the commissioners of the regional housing authority each also find that (because of the aforesaid changed facts) the purposes of this Housing Authorities Law could be carried out more efficiently or economically in such county or counties if the area of operation of the regional housing authority did not include such county or counties. Any property held by a regional housing authority within a county or counties excluded from the area of operation of such authority, as herein provided, shall (as soon as practicable after the exclusion of the county or counties respectively) be disposed of by such authority in the public interest.