According to an article on the Japanese gaming website 4Gamer.net, the characters in the Metal Gear Solid Ground Zeroes video can be heard talking about Chico and Paz, as well as Mother Base. Furthermore, the voice of Tomokazu Sugita can be heard, who is the Japanese voice actor for Miller in Peace Walker.
Of course this doesn’t necessarily mean that any or all of them are in the game, but they seem to play a part in the story at least.
The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.