Forgot to come back and report on the water tightness. I've been in a couple of rain storms and washed the bike a couple of times. Never even thought about water leaking in. Opened it the other day to retrieve one of the tools I keep in there and everything was bone dry, no evidence of a leak of any kind. My registration and insurance papers looked like they had been perfectly stored in a desk drawer.
People do seem to think that the covered key lock is an electrical socket of some kind. I was rather easily able to convince one of my coworkers (an engineer embarrassingly) that it was the battery pack for the plug-in hybrid drive system. He just nodded and said "cool", didn't question it at all!