Coincidence? Probably, though it sure looks strange as the companies struggle to agree on a carriage deal that would prevent CBS stations from going dark on TWC systems in New York, Los Angeles and Dallas as early as Monday. That didn’t stop CBS from saying this afternoon that it will add $5.1B to its share-epurchase program, bringing it to $6B. And Time Warner Cable announced a $4B authorization, about an hour after it announced that CEO Glenn Britt will step down at year’s end. He called it “yet another signal of our confidence in our business.” The two announcements probably aren’t related, says Wells Fargo Securities’ Marci Ryvicker. She finds TWC’s decision especially “curious,” though. Even though it was about time for the No. 2 cable company to announce a new authorization, “we can’t help but think the timing a little strange” — perhaps as a way to raise the stock price and “thwart a potential takeover attempt” by Charter Communications. Its biggest investor, Liberty Media’s John Malone, is salivating over the prospect of buying TWC, though Britt is cool to the idea.