If your cutting real plaster, good luck. Your carbide chain if you would spend that kind of money wont last long imo. Cutting plaster is like going outside and trying to cut a piece of sandstone in the back yard. Sawzall blades dont seem to last long at all, and at $3/ea and up, that gets expensive real fast. If the cuts have to be perfectly straight, then use the sawzall but get ready to change the blade every few feet.
I would just beat it out with a sledge, pickaxe, fire axe, ect. If your gutting a place like it sounds like, just beat it all out. You could also try beating a hole in it, and using a very heavy roofing shovel to pry the lath away from the studs/joists bringing the plaster with it. There is simply no nice way to remove plaster.
If you have to cut it, use a circular saw to cut through the plaster with a diamond blade, then go back witht a sawzall for the lath. If you try to cut the lath with a cutoff wheel from anything, all your going to accomplish is setting a fire.