(2) No employee retirement or pension plan may exclude any employee from membership in such plan or cease or reduce the employee's benefit accruals or allocations under such plan on the basis of age. The provisions of this subdivision shall be applicable to plan years beginning on or after January 1, 1988, except that for any collectively bargained plan this subdivision shall be applicable on the earlier of (A) January 1, 1990, or (B) the later of (i) the expiration date of the collective bargaining agreement, or (ii) January 1, 1988.
(3) The provisions of this section concerning age shall not prohibit an employer from requiring medical examinations for employees for the purpose of determining such employees' physical qualification for continued employment.
(4) Any employee who continues employment beyond the normal retirement age in the applicable retirement or pension plan shall give notice of intent to retire, in writing, to such employee's employer not less than thirty days prior to the date of such retirement.