Oh okay, I see now. That DOES look like a some light entity over the model, but it looks like it's been played with a bit. Very interesting, I'll try experimenting with some of the values and get back to you. But for now, I'm pretty stumped on how that specific look is achieved. I'm sure someone with a proper answer can chime in.
EDIT: Here's something to try! (It won't turn out the same way though) Maybe create a block over the light bulb using any light texture, THEN create an info_texlight that references that block's texture as the key. That way, the block glowing could pretend to be the bulb's glow. Of course you would shape the block to be more of a sphere, but I think you get the idea.