I think the weatherization is under the tiles. I'm not sure what they'll be doing, but I imagine there will be forms of some kind under the tiles to cope with wiring concerns and alignment, and there will be weather protection underneath those forms. Some of the weather sealing will fail, same as the tar/sheeting does on conventional roofing. The tiles should still be good, so the main cost after 30y should be labor to re-seat and re-seal, and the optional replacement of any failed solar tiles.