Looks like it just started today.
I'm assuming this is the replacement for the SiriusXM channel.
Big 12 Conference and TuneIn Launch ‘Big 12 Radio’ to Bring College Sports Fans Non-Stop Conference Coverage
Beginning today, fans can access 24/7 coverage of the Big 12 Conference on new dedicated station, featuring daily Big 12 sports talk, live games and exclusive coach and player interviews
big12sports.com
I'm assuming this is the replacement for the SiriusXM channel.