Ghost/hologram shader?

I'm curious if there's a shader in the Source engine that would allow for a ghost effect, where the entire model is rendered at a certain opacity level relative to everything else. Compared to what happens with, say, the holograms in Half-Life's hazard course, where you can see where polygons overlap on concave shapes.

The ability to receive lighting from the map is optional, but appreciated.

And yes, I checked the wiki. I didn't see anything of the sort, but I know it's not comprehensive.

Those pictures look like it has the same problem as the Half-Life holograms, though it would be easier to tell if it weren't all one color.