I think you meant to say lath and thin set. I do not believe your local building department has an opinion on that method, or even cares how floor tiles are set.
It's called "scratch-coat" and "Jersey mud job", and I can tell you it's a terrible method. It has failed every test it's been subjected to when done under controlled conditions. However, it is very popular in your area of Canada. Why do many tile jockeys do it that way? It's easier and cheaper to do.
Results? You're likely to have hairline cracks in the grout within the first season, (but may not know it). Long term,..... high failure rate can be expected.
If you wanna do it right let us know.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.