My Experience: I have a 2006 BMW 530Xi Wagon. Two days ago my radio and Navigation stopped working so i dropped it by Rasmussen BMW in Portland to have it looked at. I got a call from the service advisor saying that one of my drains was partially clogged and the water ended up being re-routed into the body panels causing damage to the headliner and all of the electrical equipment, NAV, RADIO ETC. He mentioned it was not covered by the warranty because the owner needed to maintain the cleaning of the sunroof drain tubes. I immediately said, i paid for the 100K extended warranty AND Maintenance plan. Originally, I was told when buying the maintenance plan that i only needed to take care of the rubber (TIRES) and all other maintenance aspects were handled by BMW. I have been very diligent about taking the car into the dealership and on three ocassions had Rasmussen adjust the sunroof due to noise issues, i assum this would have been a good time to perform maintenance on the drain tubes. The service manager at Rasmussen explained that the cleaning of the sunroof drain tubes is not a maintenance item, and that cleaning the tubes is the owners responsibility....(WTF). I explained there are many other owners of my exact car having the same issue and there are many service bulletins available discussing issues with the drain system in the bmw. The service advisor explained these SB are to fix other issues and are not related to my issue.
So BMW will take care of changing my wiper blades, flushing my coolant, oil, etc....but when it comes to flushing the drain tubes its an owners responsibility..*****. This is the 11th car i have owned, all with sunroofs, this has never been an issue with any. I live in a secured buildin and park my car indoors, so its not like it sits under a tree all day.
I did call BMW north america and had discussions with them, but received the same bull**** I did from the dealership.
I hope this information helps you in some way.