Just tried it the first time and it works fine. You have to use the Firefly, it won't work with the P4 render thingie and I noticed that you have to change the colors from black to anything else. When the background color stays dark in the BG color node (or is it a shader or ... ????) you will see no change. And don't ask me what I did there, I just changed the colors, plugged something together and this is what came out :-).

Every organisation rests upon a mountain of secrets ~ Julian Assange