According to Joe Reedy with the Cincinnati Enquirer, CBS protected Cincinnati's Week 16 game against the Pittsburgh Steelers, which is quietly (though noticably) figuring to become a game with massive postseason implications for both teams.
The league has already announced that no games will be flexed in Week 14 or 15, leaving the only possibility for an impromtu Bengals prime time game Week 17 against the Ravens.
Yet that game could be protected as well. There won't be any interest with Bills-Jets, Titans-Jaguars or Raiders-Chargers. We don't see much interest in Chiefs-Broncos either, compared to the remaining AFC schedule. The Patriots-Dophins, Colts-Texans and even Ravens-Bengals have first and second seed implications facing teams with a chance at the Wild Card. At least right now -- anything can happen in a month.
One thing that could -- though we doubt by much -- impact the decision is that the Bengals and Ravens had already played a primetime game this year (which didn't turn out too good).
The NFL utilizes "flexible scheduling" on Sundays in Weeks 11-17. Flexible scheduling will ensure quality matchups in all NFL Sunday time slots in those weeks and give teams a chance to play their way onto primetime and into the late-afternoon 4:25 PM ET time slot on CBS and FOX.