The motor unit must be accessible but they do make remote mount lift motors that use pulley's to change angles and guide the cable to a space nearby.

I just installed an Aladdin 200 unit over the weekend. Very cool, and should prolong my life by avoiding dragging out the 10 foot stepladder twice a year to clear the chandelier. In my case the install was in a standard attic space above the foyer. As dim says they make remote pulley versions but you still need limited access to the area above the current ceiling box. Check out the link below for the instructions.

Here is a link that might be useful: Remote install