"Mas Oyama was a huge advocate of breaking. The guy just loved to break **** with his hands. Breaking remains to be a cornerstone of Kyoukushin. We all love KK here, right?"
Our sensei was telling us over beers a few months back that, in his later years, Oyama practiced breaking opponents' elbows as part of a trap/block against straight punches. As he was telling us, though, it's not something you can practice much at full force.
And yes, it seems we pretty much all love KK here. Oddly enough, though, although breaking is heavily featured at big KK tournaments, individual dojos seem to have complete leeway in deciding how much to practice it.