Interiors: MirrorSurface translucency

We're trying to create translucent mirrors. We've managed to get reflective interiors into the engine, but if we assign translucency to the MirrorSurface entity in the map editor, the reflection seems to blend with the fog color instead of with the texture that the surface could have.

Any thoughts on how we can get the reflection to properly blend with the surface's texture?

Also, we want to have several mirrors in a scene. Ordinarily, this would presumably kill the framerate, but they're all on the same plane, so theoretically it should be possible to render the reflection only once. How difficult would it be to modify the reflection code to make something like that work?

Thanks in advance for your help!