Problem with T-cut is, that it actually removes a layer of the material that your using it on, just like on the paint of your car.
What's more of concern, that with a car you need to seal in the shine, and reapply wax every now and then, otherwise the paint will go dull again, because you've removed the last bit of top protective lacquer .
With a window, if there is any protective layer on the glass, you've essentially removed it, and in the long run, might actually damage the windows far more then lime scale could ever do.
Not so with MDR, it just removes the limescale, and nothing else.
I would be very wary with using something like T-cut on anything else then your cars old paint.