Hi RomasNoreika, I must admit that I was wrong. It seems there is some problem with reflecting light mtl with emit light off, or self illuminated materials. The reflections are there, but it looks like they are extremely hard to sample, which results in noisy mess. I have this reproduced, and I will report it straight to the devs. Sorry, I was sure that the result will be different, without actually checking it...
note to self: Tests\light-specular