From some experience working in broadcasting, the feed would've been cut no more than a second after going out, if going out at all; you can see what you're going to cut to before you cut, and it's not a one man job. You don't just press play and go grab some coffee until the next show starts, a whole team actively watches a wall full of monitors, consisting of live feeds, queued feeds, a series of playback machines, the feed being sent out before it's sent, and the feed being sent out after it's sent.
The only circumstance where another show could be sent out would be downstream of the broadcast station, therefore not a responsibility of CNN but instead a cable/satellite provider- which often also have feeds back to the broadcast station for further verification.
edit: it's also viewed by upstream supervisors at another location inbetween leaving the broadcast room and going public, who also have the ability to cut the feed.
