NOTE: If mine is not the same issue, I will delete my posts to avoid steering the topic elsewhere.
Sorry, what I meant by lights was an actual light mesh lol.
So a material with an emissive value, like what you have there, with colour linked to emissive. I don’t mean actual light objects.
So if I put a decal over the mesh that has emissive material, the decal is visible, except for where the emissive material is.
Like this:
http://i.imgur.com/KqVR93w.jpg
With a very simple emissive material (this is the orange light material):