We’re experiencing the same issue with UE 4.10 and Maya 2016. Exporting FBX from UE4 and importing them into Maya for modification, and then exporting them back into Unreal loses some materials for whatever reason. Normal export of meshes from Maya into Unreal works fine.
The reason we are using this is because sometimes we don’t have the access to the original source of the models (person is unavailable, model is missing in repository, etc, there’s dozens of reason) and it’s really important for us to be able to properly export FBX from unreal.
Another usercase is when we need to adapt a model to some in-game geometry, where you can’t help but to export several models from within the level in order to get their correct layout and intersections with each other.