It can work for bones but for blendshapes?
I heard that Adobe supports Unity in that case, they created the plugin called FacePlus or somothing like that, that enables seamless facial motion capture in game engine. Oh God, that would be perfect in UE4 
Anyway, I can animate my face in blender when I import dae from fuse but my retargeted skeleton refers only to the body, so I am not sure if it is possible to apply a blendshape animation into my character. I was thinking about some methods to animate the blendshapes in UE.
But I will try it to confirm the theory.