May I suggest that in this thread, the term MCT is ambiguous, and instead, Max Climb or Max Continuous should be spelled out.
Max Continuous is a certified rating; the certifying agency FAA/JAA/etc has been satisfactorily shown that the engine will run all day at Max Con as long as fuel and oil hold out. It is intended for OEI or similar unusual situations.
Max Climb is a limit imposed by the OEM for warranty purposes; Its intent is to maintain parts life to expected levels, preventing premature engine removals.
Max Climb is less than Max Con at low altitudes, of course. But engines may have performance curves that slowly increase Max Climb as the bird climbs, so at TOC Max Climb may actually converge with Max Con. If so, this is intentionally done to meet climb profile requirements.