Yes, I grew Sudachi and Changsha in Ticino near Lago Maggiore on 600m above sea level. We had regular freezes down to -10C, -12C in 2006 and 2012. Both plants survived without any damages.
I now moved on the northern side of the Alps near Lake of Constance and started with Ichangquat 11C in ground. It is doing fine without any protection and grows nicely. First fruit appeared last year.
The big difference between both locations is the type of frost. Ticino has clear and sunny skies almost all winter and frost mostly is radiation frost. Temperatures rarely stay below freezing during the day (only a handful of days per year). In the North, cold winds from the East bring advective frost. Absolute minimum temperatures don't differ much from Ticino but when the "beast from the East" comes, temperatures stay well below freezing for several days in a row. You have to choose a spot which is well sheltered against wind from East and North. Living a few hundred metres from a large lake also helps buffering cold temperatures.
I am currently testing an Ichangensis x sinensis cross from Eisenhut (Z194:
http://www.eisenhut.ch/pflanzenmenue-e/index.php?id=285348&q=ichangensis&orderby=abc&modus=liste) on the western wall of the house.