The Secretary shall, at the request of a State made before January 1, 1970, or during 1981 or after 1988, enter into an agreement with such State pursuant to which all eligible individuals in either of the coverage groups described in subsection (b) (as specified in the agreement) will be enrolled under the program established by this part.
For purposes of this section, an individual shall be treated as an eligible individual only if he is an eligible individual (within the meaning of section 1395o of this title) on the date an agreement covering him is entered into under subsection (a) or he becomes an eligible individual (within the meaning of such section) at any time after such date; and he shall be treated as receiving money payments described in subsection (b) if he receives such payments for the month in which the agreement is entered into or any month thereafter.
Any individual whose coverage period attributable to the State agreement is terminated pursuant to subsection (d)(3) shall be deemed for purposes of this part (including the continuation of his coverage period under this part) to have enrolled under section 1395p of this title in the initial general enrollment period provided by section 1395p(c) of this title. The coverage period under this part of any such individual who (in the last month of his coverage period attributable to the State agreement or in any of the following six months) files notice that he no longer wishes to participate in the insurance program established by this part, shall terminate at the close of the month in which the notice is filed.
With respect to eligible individuals receiving money payments under the plan of a State approved under subchapter I, X, XIV, or XVI, or part A of subchapter IV, or eligible to receive medical assistance under the plan of such State approved under subchapter XIX, if the agreement entered into under this section so provides, the term “carrier” as defined in section 1395u(f)  of this title also includes the State agency, specified in such agreement, which administers or supervises the administration of the plan of such State approved under subchapter I, XVI, or XIX. The agreement shall also contain such provisions as will facilitate the financial transactions of the State and the carrier with respect to deductions, coinsurance, and otherwise, and as will lead to economy and efficiency of operation, with respect to individuals receiving money payments under plans of the State approved under subchapters I, X, XIV, and XVI, and part A of subchapter IV, and individuals eligible to receive medical assistance under the plan of the State approved under subchapter XIX.