I have a Chorus Triple 53/42/30 and a Centaur 13-29 10sp cassette, and I run a Chorus medium cage rear mech. All works beautifully. Capacity of my system is (29-13)+(53-30) = 39.
I will be buying the new 2013 Centaur cassette with 12-30 as soon as I can hold of one, and with experimentation, I am confident that all will be well. Capacity of that system will be (30-12)+(53-30) = 41 and I reckon that would be the max capacity that my medium cage will take. If I wanted to fit a wider cassette, I'd need a long cage.
The max tooth size that Campagnolo can handle at the rear is possibly 32t, but having not tried it, I cannot be sure.
Hope that helps.