I haven't had much of a problem with "Shimano" brake cables jamming in my Campy levers but you MUST use Campy style shift cables or they WILL jam and be almost impossible to get out. When I did this I had to take the lever apart and almost broke it trying to get the cable out.

I would not bother with "genuine Campagnolo" cables. Lots of people make good cables with the Campy head.