The question of Soviet response to the Apollo missions occasionaly arises in the context of hoax theories. While gathering stuff on the history of astronomy from space, I came across a little book "Ryadom so Zvezdami" ("Near the stars") by Pyotr Klimuk, veteran of Soyuz 13 and flights to Salyuts 4 and 6. The book was evidently written in late 1977 (press date 1979). Starting on the first page of chapter 1, he muses (my quick translation):

"By now twenty years have passed. Only twenty! In this short span - an instant i the history of civilization - we saw the far side of the Moon, received signals from human apparatus on other planets, looked on a televised panorama of the "evening star" Venus, and performed analysis of the lunar surface. Above all, in this time humanity began to live in space: there, thrown into weightlessness, he welded metal and raised plants, so that, from beyond the atmosphere, he conversed with Earth via television, laying the groundwork for international cooperation in space.

...And we all watched on television as man took his first steps on the surface of the Moon; watched, delighted but not, if you please, surprised..."

So, in a book distinctly not intended for international consumption, cosmonauts understood the Apollo landings to have actually taken place, as of a few years afterward. I"ll mentally file that with the article from Novosti Kosmonavtiki about Soviet tracking and signal reception from Apollo lunar missions.