may carry out a mobility demonstration program to enable public housing agencies to administer housing choice voucher assistance under section 8(o) of the United States Housing Act of 1937 ( 42 U.S.C. 1437f(o) ) in a manner designed to encourage families receiving such voucher assistance to move to lower-poverty areas and expand access to opportunity areas. (b) Selection of PHAs (1) Requirements The Secretary shall establish requirements for public housing agencies to participate in the demonstration program under this section, which shall provide that the following public housing agencies may participate: (A) Public housing agencies that together— (i) serve areas with high concentrations of holders of rental assistance vouchers under section 8(o) of the United States Housing Act of 1937 ( 42 U.S.C. 1437f(o) ) in poor, low-opportunity neighborhoods