[Fwirt]

Looks like the bottle is pushed up from the bottom (so the water won't pool around the joint) and then caulked with some kind of sealant. Since these are basically shanties with corrugated steel roofs I would think that leaks would be the least of your concerns. And since plastic bottles come from the waste stream anyway I doubt that replacement after a few years would be an issue. Depends on what happens after a few years of UV exposure... if the main problem is just the plastic becoming hazy, well, that just gives you a free light diffuser!