The only employees of the University of Maryland Medical System Corporation who are eligible to participate in the employees’ systems under this subtitle are employees who were: members of an employees’ system; and employees of the University of Maryland on June 30, 1988, who became Medical System Corporation employees on or before July 1, 1988; employees of the University of Maryland System on June 30, 1990, who voluntarily became Medical System Corporation employees on or before July 1, 1991; or Montebello University employees as defined in § 13-401(g) of the Education Article who were employees of the University of Maryland on June 30, 1992, and who became employees of the University of Maryland Medical System Corporation in accordance with § 13-404 of the Education Article.