Glass and Mirrors - taping then breaking part of mirror

I asked a question about my mirror before but now I have another question as a possible solution for me. Ok, I have a large mirror in my bathroom which has a cut out about 6 inches from the top where my lights are. I want to remove those lights and replace them and also add a frame around the mirror with Mirror Mates. I was told by someone on this website that I have to remove the mirror and take it to be cut. What would happen if I taped the mirror with a lot of masking tape -- like people tape up windows and glass sliding doors to protect them from shattering if they broke when a hurricane comes. So, if I tape up the mirror except the part that I would like to break off, could I possibly break that part off, remove the tape, have a new light fixture installed and install the Mirror Mate that would cover any raggedy edges on the top? I know I probably haven't explained this very well.

The principle of cutting glass makes it impossible to do what you are trying to do. Glass is scored on the surface (the side facing the room) and be broken out from the opposite side (the side facing the wall) of the score. You can see why this is impossible to do with the mirror in place.