James, a cold planer would probably do the job. It might give you some bounce from the ceramic tile since the tile will break up unevenly, but it should run through the mortar bed pretty easily. Check out
http://www.abcgroff.com/ic/ssattach.htm for some info. If the planer isn't the thing, you might try a spade bit on a small breaker attachment. It wont give you the width of cut, but it works pretty well.
Bulk Removal Machine
Linear Mode
