Then how do you power a ceiling mounted projector if you can't have a receptacle above the acoustical ceiling?
Typically, receptacles installed within the ceiling cavity of drop ceilings are generally for maintenance work so one can plug in a drop light or possibly a power tool, such as a sawzall/drill.
what about power supply cabinates (120v input 24v output) that are not temporary, dont require any interchange, and do not require removal for maintenance or repair, can these be cord and plug connected? I say no, others say yes
Those usually shouldn't be above a regular ceiling grid at all anyway, since 110.26(A)(1)(b) requires written consent from the AHJ for working space depths smaller than T110.26(A)(1), and one could still say that the width must be at least 30".
Not that anyone has ever been called on that, though.