It's curious that the instructions I received from fellow owners elsewhere on this K12/1300GT forum (see the thread titled "BMW Float Charger" -- at http://www.k-bikes.com/forums/showthread.php?t=19993
-- that ran Oct. 23-25) differ slightly from those you mention, ugly. They are:
Start with the charger not plugged into an electrical outlet.
Plug the charger into your bike's accessory socket,
Turn on the ignition (so the CanBus system can recognize the charger once it's plugged into the electrical outlet),
Plug the charger into a wall electrical outlet,
Turn off the ignition.
In other words, these instructions are to not
turn the ignition on until after you've plugged the charger into the bike. It's hard to believe it matters one way or the other, but I did have to follow these steps to get mine to work properly.
(However, I noticed today that, after more than two weeks of having the green light illuminated -- indicating a full charge -- the yellow 2/3 charge light is now on. Don't know what to make of that.)
By the way, the dealership that sold me my charger did tell me that if the garage is, like mine, attached to the house in such a way (partially tucked insdie the borders of the house itself) that it's not likely for the temperature inside it to get below freezing, the battery will be okay; if it gets below freezing, all bets are off.