Welcome to the world of remodeling,...there is no easy way. A diamond blade on a cuttoff saw , wormdrive or skillsaw will cut through the tile and concrete, but gets buggered up on the metal lath in the corners. And what a mess it makes when cutting, the dust is unbelievable. If you want to avoid the dust, Then you need a wet cutting saw with a GFCI switch, or plug into one.
We always do it the old fashioned way, hammers with a hardened chisel to bang into any corners, or if you have a commpressor that is big enough, use an air chisel Next are crowbars and sawzall to cut the metal.
wear a dust mask and the goggle saftey glasses.