I have obtained and operated a Part 141 school and as an Inspector had oversight of a Part 141 school.
First of all, their is no "maintenance requirements dictated by the FAA in their operations certificate". The "operating certificate" simply states the name of the school, address, FAA assigned number and it grants them the privileged to operate as a provisional or full part 141.
The only mention for aircraft maintenance comes here:
14 CFR 141.39 Aircraft
(a)(3) Is maintained and inspected in accordance with the requirements for aircraft operated for hire under part 91, subpart E, of this chapter;
(b)(3) Is maintained and inspected in accordance with the requirements for aircraft operated for hire under part 91, subpart E of this chapter, or in accordance with equivalent maintenance and inspection from the foreign aviation authority's requirements;
So there is no "approval of a maintenance plan" as long as the operator can show he complies with the applicable provisions of 14 CFR Part 91.