MLB "Extra Innings" add-on

Has anyone used the "MLB Extra Innings" add-on and successfully viewed St. Louis Cardinals baseball games throughout the regular season? I do not want to switch to DirecTV but will to get Fox Sports Midwest if necessary. I'm told by the Cox reps this works for all Cardinal games not being broadcast on ESPN, ESPN2, Fox Sports 1, or MLB Network. Any validation of this would be greatly appreciated!