35 Pa. Stat. § 1595.6a
For the purpose of cooperating with and assisting counties, cities, boroughs and incorporated towns, a housing authority may exercise its powers in the territory within the boundaries of any county, city, borough or incorporated town not included in the area in which such housing authority is then authorized to function, or in any designated portion of such territory after the governing body of such county, city, borough or incorporated town, as the case may be, adopts a resolution declaring that there is a need for an authority to function in such territory or in such designated portion thereof. If a housing authority has previously been authorized to exercise its powers in such territory or designated portion, such a resolution shall not be adopted unless such housing authority finds that ultimate economy would thereby be promoted, and such housing authority shall not initiate any housing project in such territory or designated portion after the adoption of such a resolution.
35 P.S. § 1595.6a