I see no reason why they couldn't be transferred even if Sabu successfully bred one or two of the girls.
At this point, I will only believe Rudy is pregnant if Columbus announces she is. I have found zero indication that she was even interested in Sabu, while Sunny is always close to him and has been confirmed to have been bred several times. As for Phoebe, she has been naturally bred before so I wouldn't be surprised if she had a calf naturally from Sabu.
Even assuming Rudy and Sunny both established themselves as breeders, bringing in Joy would secure a younger female for the breeding program that Columbus lost with Ellie. Not to mention that Tucker would just be the perfect candidate for Cbus' next breeding bull. Moving just Tucker is also an option, but when Houston's herd already will be needing split AND Joy has an existing breeding reccomendation, this move kills two birds with one stone so to speak. Not to mention how well it would work for Nelson and Frankie to potentially move to Cinci's bachelor herd down the line as a pair.
I can't think of a more perfect move for half of Houston's herd. By the time this would all would likely occur; Teddy, Nelson and Winnie will be weaned, likely Shanti's hypothetical future calf would be given time to grow up a bit. Any hypothetical calves in Columbus by that time will be a little older as well. Phoebe and Shanti would easily be considered post reproductive, leaving Columbus with a solid two or three breeding females AND a valuable young bull to move forward.
Connie and Hank would still work as their seperate group until she passes, but then Hank could either serve as a temporary mentor to Nelson and Frankie or be moved out himself (Once Groucho dies in Denver, Hank, as a friendly bull in his own right, would be a great choice to guide any future young bulls at the facility).