Here is what I found:
Here's the rule cut and pasted from the NCAA Rule Book:
"Rule 5, Sec. 7 (page 91)
Art. 1. Each period shall begin when the ball becomes live.
Art. 2. Each period shall end when the red light or LED lights have become
activated. When the light fails to operate or is not visible, each period shall
end with the sounding of the game-clock horn.
a. In games when the red light is not present, the game-clock horn shall
terminate players’ activity.
b. In games with a 10th-of-a-second game clock display and where an
official courtside monitor is used, the reading of zeros on the game
clock is to be used to determine whether a try for goal occurred
before or after the expiration of time in any period.
When the game clock is not visible, the officials shall verify the original call
with the use of the red/LED light(s). When the red/LED light(s) are not
visible, the sounding of the game-clock horn shall be utilized. When
definitive information is unattainable with the use of the monitor, the
original call stands."
So -- to recap the official rule...the order of importance for ruling an end game shot...
-1st -- if the refs rule the game over and there is no controversy -- then it's over
-2nd, if there is a controversy or buzzer beater play, then it is the replay video of the game clock that determines the call
-3rd if the clock or video are not available, then it is the referee's judgement regarding the lights on the backboard
-then finally, only if both those other sources are unavailable or fail, then use it falls to the referee's judgment on whether the play beat the horn.