You =can= parse the BSP file manually without too much trouble. Long time ago I released a public demo that parsed out lights and area volumes and reintroduced them into the map as sprites and alpha'd cubes but I can't find it at the mo. I'l do some more digging if you're interested in this approach.
[EDIT] found it here. [/EDIT]
[EDIT] found it here. [/EDIT]