Hello,
Like others here, I have a new factory taillight assembly for the 2011 Fit to replace a broken one. The only attachment points are the three bolts on the back. I see no screw holes on the bottom. The plastic panel on the back has a few alignment posts. The only potentially problematic piece I can see is a thin, 3 by 1/4 inch plastic piece on the bottom with a small protruding tab at each end. So is it still necessary to remove the bumper?

My guess is that the old one might be hard to get out without breaking the tabs on the bottom, but the new one will just snap in place.

 

on 2011 Fit, there is no need to remove the bumper. Simply:
1) open access plastic access panel behind the taillight; car key works fine as noted by first post above.
2) press tab and pull out the three wiring connectors from the light. If you have big fingers, a bent needle-nosed pliers works for this. It makes sense to note which connector goes where as you detach them, although they are different sizes so can't hook them up wrong.
3) I also detached the ground wire, to make it easier to get to the nuts, but it is not necessary.
4) remove nuts from 3 bolts (need small 8mm wrench or socket) The top nut is a bit difficult to reach with a socket.
5) pull off the assembly
6) push new assembly in place. Hold it tight to the body as you replace and tighten the nuts.
thats it