(a) Except as provided in paragraph (b), no disability benefit is payable from the retirement plan.
(b) The disability benefit coverage for a fire department in the monthly division is the disability service pension amount specified in the retirement benefit plan document applicable to the former relief association affiliated with the fire department and in effect as of the last day before the date on which retirement coverage transferred to the retirement plan, subject to all conditions and limitations in the disability service pension specified therein.