I had a similar one a whiule back excess wire under kitchen units, told builder i won't be tiling floor, thats ok then he said i'll cut the wire! i walked off until correct mat was installed 2 days later.
I had spme porcelain tiles earlier this year and could not get them to cut with anything, put a stop to the job as they were quite expensive customer went back to where they got them from, turns out they were a problem tile had the whole lot refunded.