System Information
Mac OSX 10.6

Blender Version
Broken: 2.74 dc15860

Short description of error
When rendering with Blender Internal, light emission from volumetric materials is not included in the "emit" render pass. This makes for very difficult work when attempting to composite a fire+smoke simulation render with another image. I understand that Blender Internal isn't high on the priority list, and there may be some deficiency in the existing code that would make this a pain to fix. However, it would be quite helpful if this gets fixed.

Exact steps for others to reproduce the error
This is pretty simple to see. Open the attached .blend, and render. In the image viewer (bottom left), the composite result is displayed, and you should see three cubes. One has an emissive volume material, one has a non-emissive volume, and the third has an emissive surface material. In the node editor (top), the emit pass is displayed on the backdrop. Here, only the emission from the third cube is displayed, while the emission from the first cube is missing.