Notwithstanding section
411, a multiemployer plan in reorganization may be amended, in accordance with this section, to reduce or eliminate accrued benefits attributable to employer contributions which, under section 4022A(b) of the Employee Retirement Income Security Act of 1974, are not eligible for the Pension Benefit Guaranty Corporation’s guarantee. The preceding sentence shall only apply to accrued benefits under plan amendments (or plans) adopted after March 26, 1980, or under collective bargaining agreement entered into after March 26, 1980.