Tom Boonen used Campy 10-speed cranks and front derailleur with 11-speed rear derailleur and cassette at Paris-Roubaix. Seemed to work for him.
Good information to know - thanks.
I've been hearing/reading that a Campy 10 speed crankset would work with the Campy 11 speed drivetrain and I guess (by extension) other cranksets should work as well.