Some would say no to your question and it is on the fine line by definition.
Accessible (as applied to wiring methods). Capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building.
Being that the fan is structually attached and "blocking" the box would be the argument. However by simplify the situation, what is the difference bewteen the fan and an access panel that is held on by screws?
If I were the inpector, I would say if would be allowed only if there was no practial way of refeeding the power to the fan.
