You will have to put the tile in first then cut the box in no matter how you secure it.
I have done it both ways. Framed down from the hard ceiling, and used those chain kits. You can do it no other way than to put the tile in first.
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.