I don't think that dbus switchboard works that way - last I checked dbus switchboard let you take a file-type and create an association, through some dbus linked voodoo, which tells the N900 which program to open that filetype with. I don't think that the dbus switchboard can create an association for the "lens cover opened" dbus message(s).

The process might be similar, but I don't think that's what dbus switchboard does.