Trust me, these are WiFi repeaters. I remember times when they werent't there over the balconies, and WiFi signal was unusable or at least very poor on the balconies. Princess changed that fleetwide for the MedallionNet.
No, not thick cables, they are just carrying a lot of paint, like everythink on the outside. Plugs - hm, outside in sea conditions, of course this can be 12v plugs.