Ok full disclaimer this is my experience but I'm not going to recommend anyone try this.
I incorrectly installed the gear cable in an 11 speed Athena ultra shift lever, the cable missed the hole in the index gear and the cable end got lost in the mechanism and for the life of me I couldn't retrieve it, I could see it but it was stuck. Being impatient to get riding I started to dismantle the lever mechanism from the handle bar end. The central pivot bolt can be removed with a 3mm allen key. I carefully removed each part in order making sure to remember the order until I was able to dislodge the cable end. Replacing the coil spring was tricky but I found if I hooked the end of the spring on the locater, when I replaced the remaining parts and retightened the pivot bolt the spring re tensioned fully and snapped into position.
I think the levers are serviceable however Campagnolo isn't selling the individual parts.
http://www.youtube.com/watch?v=5Nr35wCxlFsBe careful because I think dumb luck worked in my favour.
Peter