Actually the person who said to do it using a camera has the right idea, you all just misinterpreted it.
If mirrors were implemented none of that would be happening serverside. Only clientside. It's called render-to-texture - if you've played GMod, RT Camera tool and RT screens (there's a few in the PHX modelpack, I believe).
Think of it like this. Look at your screen in Blockland. Imagine that you are looking out from the mirror. What you see is textured onto the mirror. It's a perfectly feasible thing to do (for safety's sake, recursion limits are often in place, like RT cameras not rendering RT textures).
However it's not possible with just Torquescript, it would require implementation within the engine which, as we all know from experience, Badspot will never do.
If you want to do mirrors for filming, get a second person to get their camera inside of the mirror facing out, have them film the scene, and composite the resulting video onto the mirror's surface in the regular video.