I reminded the SA about the rear drains when he called with a status update and he said the tech ran water through the drains and made sure it was exiting the vehicle at the right point.

As for "not knowing that a outside influenced compromised the system," isn't that part of the diagnostic procedure? e.g., if the owner says he's been doing one thing, and the computer says he was doing something different, shouldn't a good tech ask themselves, "Hummm, I wonder what possibilities might be causing the computer to report that information if he isn't doing it?"

But I'm still not sure that the water issue is a bad trunk gasket, so I will now proactively and periodically check the area for water accumulation.

I found the part about notifying BMW they need to revise their test plan because it gave a false indication of a "good" battery interesting.