A new 11 speed Shimano RD, such as RD-5800-GS, might also work according to some of the actuation ratio charts, but I don't recall anyone ever testing it. I have one sitting around for that purpose, but never got around to testing it myself, since the Campy bike has the Campy wheels. 11s Shimano cassettes won't fit on 10s Shimano wheels.
I tried it recently, a 5800-SS rear derailleur with 2009 Centaur 10 speed UltraShift shifters and a 105 5600 12-25 cassette, but didn't have any luck. The variation in cable pull across each shift for Campy (being 5x2.5mm, then 2x3mm, then 2x3.5mm) meant that shifting was comprimised at one end of the cassette. If the cable was too tight, it would shift fine on the smaller cogs but pull too much for the bigger cogs, and likewise if it was too loose it would shift poorly on the smaller cogs but just fine on the bigger cogs.
However, my mechanical ability is pretty crap on the best of days, and I'd be interested to see how it works for someone with more aptitude than me. Supposedly Srampagnolo works fine (Campy 10-speed shifter, SRAM road RD and Shimano/SRAM 10 speed cassette), and if anything, the 11 speed Shimano stuff should be more likely to work than SRAMpagnolo given the pull ratios.
If you tried at some point, I'd be interested to see your results and know if mine was just down to poor setup.
The real pity here is that Campy's 10 speed cassette choices are poor if you want low gearing. In Veloce the lowest is a 13-29 (where 50x13 is not the most pleasant highest gear to have, but bearable), but a Centaur 12-30 cassette is stupidly expensive compared to Shimano 10 speed cassettes now.