Yes  it  should  work.

Hello @mannamedbob, 

Its such a great Idea, and definitly should work, my friend in my old clan and the clan leader used to do this with Valk and Mountain King in teh 3x3 Arena, so MK would be counterattacking endlessly, especially if you have Retributaion T5 Mastery on him, however i doubt the Effectiveness of his A1 in DT Hard , beacuse the amount of the HP waves is Rediculous there. 

Alpha H

You need only look at one of the most broken champs in the game - Rotos - to see that yeah, CA does trigger extra turn.

What I'm unsure about is whether the extra turn is of your choice, or if it executes automatically - I assume it just becomes your champ's turn, though.