Originally Posted by sWe

If the UFH is covered by SLC, then sure, just be careful when you remove the old adhesive. Isolate the tile from the rest by cracking the grout. Then break the tile with a chisel and a hammer, and pick out the pieces. Then scrape or grind away enough adhesive to allow you to fix a new tile.

If the UFH is in the adhesive itself, then it'll be hard to do it without damaging the cable. Do it the same way as earlier described, but be VERY careful when you remove the old adhesive.

I tend to avoid using only adhesive to cover UFH. Not only does it make it harder to replace tiles; the distribution of heat is impaired as well.
Most manufacturers/distributors (over here) require that the cables are covered by a minimum of 12mm SLC or similar. Otherwise, any warranty is nulled.