Today’s announcement suggests that Viacom is warming to the idea of allowing its shows to appear on TV Everywhere platforms — but still with limits. The deal with AT&T doesn’t extend to mobile devices such as tablets and smartphones. U-verse video subscribers can watch streamed shows, on-demand, both in and out of home on computers by accessing the TV Everywhere sites that Viacom runs for BET, Comedy Central, MTV, Nickelodeon, Spike, and VH1. The companies curiously say that AT&T customers “may” soon be able to access the shows on mobile devices via U-verse.com and U-verse apps. Pay TV execs consider mobile, out-of-home access critical for TV Everywhere to succeed. But Viacom has been tetchy about granting these rights, in part because it’s hard to measure the audience on mobile devices. Last year Viacom sued Time Warner Cable when it provided subscribers with an iPhone app that they could use to watch cable programming at home. They settled the case, enabling Time Warner Cable customers to watch Viacom shows on mobile devices at home. Last month they announced a deal that gives Time Warner Cable customers TV Everywhere rights on computers similar to the ones in the new arrangement with AT&T.