It seems as though the phasers were being used as point-defense weapons in that shot, tearing into the fighters/missiles/drones from the Narada.
In the caps it looks as though a fighter is turning back and moving away from the Enterprise, being shot down by one of the Phaser bursts from her port array.
The images we have of the Kelvin shows her firing continued beams stretching from her all the way to the Narada and
using the pop-up arrays to shoot down the missiles.
As for canon we've seen nearly every configuration fitted to a Federation ship at some point, beam, pulse, straffing, proximity pulse, rapid fire beam, multi beam and even planetary use stun mode. They'd have trouble finding a non-canon array if they tried.