we just run the cables through next to one of the brackets where we've ground the lug off the tile, then use Ali flashband around the tile above and below to stop it rubbing on the tiles and cable tie the cables to the bracket. On slate we drill a hole, line the edges with ali flashing to stop rubbing, then cover with a strip of ali flashing from under the slate above.
I really don't see the need for fancy stuff like the deks system in most situations, and I'm not even that convinced of how water tight it will actually be, as that surely depends on how tight the rubber nipple is cut to the cable. We do use them for solar water heating pipe entry though.