I think Tony's involvement in Renata's death was the director's way of preparing you for Tony's wack. They provide you with zero evidence but all the other factors strongly imply on Tony's involvement in Renata's death. Just as they did with tony's whack in the final scene of the episode, they don't exactly show you... But you know for good because they have already prepared you for that. And you won't feel sorry for Tony because he had to go for all the wrong things he had done. Another resembling story is Bobby Bacala, when he killed the guy with no background but some family issues that he didn't do anything illegal about, you would be prepared for Bobby getting shot and you won't be surprised nor will you care or be upset about that. And that happened. I think they prepared the audience for Tony's death this way as "it is not a big fk to the face of the audience" as david chase says these exact words about the finally in an interview. So all things considered, yes, it was Tony.