The Wall fell in 1989, and in Berlin, so that's not it. And the USSR officially ended in December of 91. Judging by the weather and clothing, its definitely NOT December in Moscow.

The photo is of Arbat Street in Moscow (aka The Arbat, Old Arbat, Улица Арбат, Арбат, Старый Арбат). It was turned into a pedestrian street in the 1980s and became (particularly after Glasnost) a destination for Bohemian types. These days its mostly full of souvenir shops and tourist traps.

I don't know enough to say that this guy is definitely from the Soviet Navy, but that's an easy assumption. It totally calls to mind the famous WWII picture (though hopefully without the more...assaulty associations that have come out more recently). However, I wouldn't attempt to tie this to any sort of geopolitical event, just a lovely pic of a couple dancing to some of the omnipresent street bands on a nice day on the Arbat.

This Czech article has the photo in black and white and the caption says it's Navy Day. They attribute it to what appears to be a stock photo website. I don't see any other sailors, though, and in my experience, Navy Day is a raucous occasion with sailors everywhere, especially places like the Arbat. This Russian article also uses it as a stock photo. Both articles are from after the book was published, so it's not unlikely that they got it from the book.

You might consider emailing the photographers rather than the publisher: david@davidcturnley.com and contactpeterturnley@gmail.com. It appears to be David rather than Peter, but it's difficult to tell because his website is under construction. Some of the other pictures from the book are on Peter's website.

Edit: The bio section on the publisher's website says that Peter is the one who photographed the fall of communism in Eastern Europe, so he would likely be the one to contact.