To tell truth - it's all a bit upside down there now (at least for me).
But, emission Texture (Illumination Map) at the moment it's an Opacity map as well.
Here's an example of Matlib code for poster:
"name" : "Poster", -- Name of material
"diffuse" : "20.0,20.0,20.0,1.0", -- RGB + Alpha
"Ax" : "1",
"Ay" : "1", -- Not used
"m" : "1",
"tex_diffuse" : "bilboard_d.dds",
"tex_normal" : "",
"tex_env" : "",
"tex_opacity" : "Bilboard_op.dds" -- Here's the opacity map which also works as Emission Map, with settings above.
"tex_reflectance" : ""
So the question I have to Devs, is how to make semi-transparent illuminated texture (Afterburner, flames)?