[pushkins]

You can remove the wall tiles and add tack strip, the problem with doing this is that your adding another level (lower than the tile) and this looks kinda funky and really is not practicable.

Have the carpet layer use longer nails , he should put them in in the grout lines this will make the job a whole lot easier.

Hint: The better the padding the better the longevity and comfort of your carpet. People go cheap on the padding and wonder why the carpet doesn't last.