I find it interesting that the description for the Vibro Cannon does say "A target with an Armour Value that is hit by a Vibro Cannon always suffers a single glancing hit; do not roll for armour penetration" instead of "A target with an Armour Value that is hit by a Vibro Cannon Battery always suffers a single glancing hit; do not roll for armour penetration."
While reading other parts of the Vibro Cannon descrpition it does tend to separate between singular and plural. For a long time now I have believed the way Cabalistic does about it. Mainly due to the way the English Language works, with singular and plural being literal.
If it says "A" Vibro Cannon, it doesn't need to say "Every" vibro cannon. "A" works just as well.
Another thing to note is that GW has not FAQ'ed what it says, even though they have answered other questions about the Vibro Cannon. Yet, this question comes up often.