If my basement apartment and main unit have each their own electrical panels, can I have a junction box (located on the ceiling) in one unit that belongs to the other unit? For example, can there be a JB in the basement for a circuit that belongs in the main unit? My main concern is that the basement tenant would not be able to switch that circuit off at the basement panel even though it's located in the basement.
You can have a box and it may be required depending on number of bends. If it cannot be turned off at that location label it as such so the tenant won't try using it.