Said board of trustees heretofore provided for shall be a corporation and shall possess the usual powers of a corporation for public purposes, and they shall have all powers conferred upon them as conferred upon the county social welfare boards, by the laws relating to the construction, operation and maintenance of county medical care facilities. All laws governing the construction, operation and maintenance of a county medical care facility are applicable to the construction, operation and maintenance of a joint county medical care facility, unless otherwise expressly provided in this act.