I've read the other posts to this thread, and I've done this kind of work many times and never found that the expanded metal corner bead in the wall/ceiling corner to be that much of a problem.
What I did was use a plastic laminate knife (the kind with the single tungsten carbide tooth at the end of the "blade") to score deeply into the plaster along the wall/ceiling corner. I would make two such score lines; one along the wall/ceiling corner line and another about 3 inches below and parallel to the first score line. Then I'd use the laminate knife to widen the upper score line so that I could cut through the metal corner bead with a pair of tin snips. Since the metal corner bead is nailed on, and I had cut through the plaster below the corner bead, once I got one end of the corner bead exposed, I could just pull it off the wall. As long as you cut through the expanded metal right at the corner, the whole flange will pull off relatively easily up to each nail. Then you have to spend a few minutes removing the nail, and it pulls off easily until you get to the nail after that, etc.
If it were me, what I would do is remove the old tiling and see what the plaster under it looks like. If the plaster behind the tile is in good shape, I'd leave it and tile over it. If that plaster is very water damaged, I'd probably replace the water damaged plaster with 1 piece of
1/4 inch plywood covered with a 1/2 inch thick sheet of cement board (or Georgia Pacific's Denshield) and tile over that.
If the old tile was stuck on with mastic, you can remove that old hard mastic with a Nestor scraper, named after it's inventor. To make a Nestor scraper you simply grip the back edge of a single edge razor blade using the ends of the jaws of "needle nose style" locking pliers. You then use a heat gun to soften the old mastic and scrape it off the wall with the Nestor scraper. Wear a leather glove in your working hand because the Nestor scraper will get pretty hot.
Also, put a piece of scrap carpet pile side down in your tub before taking any tile off. That will protect the tub from getting all scratched up by the pieces of tile. Also, use a piece of cord and a hose clamp to fasten the cold chisel you use to remove the old tiling to your wrist. That way, if you drop the chisel, the cord will catch it before it hits the tub and causes a big chip.
I'd leave the good plaster up and tile over it. And, I'd tile right to the ceiling.
I've tiled well over 20 bathrooms, and you can see pictures of my work on my web site at:
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solidarity with the movement for change in Iran.