traderfjp wrote:
Yeah I agree if this was a floor I wouldn't even consider using the
existing cement board. However for the walls I would like to limit
the
amount of flying cement so I don't ruin the existing floor and tub.

I've replaced tile this way. After removing the tile and remaining
lumps of adhesive with hammer and chisel (most came off very easily) I
had to patch a few spots with drywall compound and sand smooth. No
problems.