Island Time, in short these switches are prewired to nothing so you can add accessories. I have read on other forums that the "hot" wires dead end somewhere within the walls of the vessel to be tapped into later.
Just so you know, a friend of mine purchased his 2001 280 a couple years ago and there were underwater transom lights, additional cockpit LED's, and a few other things wired to these accessory switches, so I know they will power something!
I have similar switches on my 300 DA and have been researching like crazy on where the wires are located for me to tap into with no luck. Hopefully I find out soon so I don't have to trace by hand...