You can tile over almost anything. That is the issue. Beautiful tile work hides bad waterproofing for a while. A shower valve that was not properly installed can hold pressure for years before it lets go. Poor drain slope does not show up until an upstairs bathroom stains the ceiling below.
Bathroom work is where a contractor's actual quality standard shows up eventually. That is why we do not sub out plumbing. Our Red Seal plumbers pressure-test every installation before tile goes on. Our electricians pull the vent fan, GFCI, and heated-floor circuits directly. We follow manufacturer waterproofing specifications exactly.
The finished bathroom looks right on move-in day. More importantly, it still looks right ten years in. That is the thing a cosmetic contractor cannot promise and that we can, because the trades holding the ceiling up are all on our payroll.
We pull trade permits directly through our licensed divisions, which removes a common stall point on bathrooms with plumbing relocations or electrical additions. One project manager, one accountable company, one 12-month workmanship commitment across every trade that touched the room.