The Verithrax was destroyed defending Coridan, right? A Federation planet? Very noble of them. However, there are some improbabilities at work here.
The Borg were destroying everything in their path, including Romulan worlds. While the Romulans assisted with defense of Federation worlds (or at least one), we don't know if that warbird stood alone or fought in conjunction with other ships, whether Federation or Romulan (or Klingon...). We don't know what weapons it used, meta or otherwise. We don't know if it was a D'Deridex-class or Valdore-type. We don't know if, perhaps, other ships kept it busy while it maneuvered for a suicide run as was depicted by some other Federation ships; perhaps by then that strategy was the only thing working, and I can see said tactic being more successful in the highly-maneuverable Valdore-type than the lumbering D'Deridex. Right now, I don't even remember if this incident was depicted in the Destiny trilogy or spoken of in one of the follow-on novels. The author was intentionally vague on specifics of the battle. Perhaps the full story is being saved up for some future "Tales Of The Destiny Event" anthology...
All we appear to know (and no, I'm not gonna leaf through the Destiny books until I find the relevant dialogue) is that this particular ship was destroyed in glorious battle defending a Federation world.
Therefore, I am disinclined to believe that metaweapons were involved for the following reasons.
(1) The Verithrax was destroyed in the encounter, which would suggest that a suicide run was involved. I can't think of a metaweapon installed on a ship that would require the destruction of the ship upon firing it or detonating it. Even the Defiant, a "metaship", so to speak, has a last-ditch weapon of several photon torpedo warheads in the deflector pod, as stated in the DS9TM; the pod can be ejected at an enemy and possibly save the rest of the ship. Yeah, I know, the metaweapon might have been damaged and couldn't be fired or activated without affecting the Verithrax, but again, Occam's Razor applies.
(2) Unless the ship was just meandering through Federation space at the time, just happening to be in the vicinity when the Borg came screaming out of the Azure Nebula, the Verithrax would have had to receive orders to venture into Federation space to intercept the Borg. And quite frankly, I don't really see the Romulans sending a metaweapon-equipped warship in harm's way just to defend a Federation planet. To defend a Romulan world, yes; Federation world, no. "Well, SicOne, maybe EVERY Romulan warship carries metaweapons!". That's indeed possible, but unlikely. In fact, I can see that possibility existing pre-"Nemesis", but after the coup and schisms in the military (like the one that led Donatra to aid the Enterprise-E), I could see them pulling all metaweapons off ships-of-the-line, with the exception of a few ships kept in close vicinity to Romulus and other very important worlds and sites in the Empire. Which leads me to...
(3) With the Borg-unchained action going on, ANY ships equipped with metaweapons would in all likelihood been ordered to Romulus immediately, to form a metablockade against the Borg. Romulus appears to certainly be very, very important to the Empire; I would imagine the Empire could exist without Romulus, but it would, I think, be akin to the old Soviet Union without Moscow. The dinosaur still lives, but it's brain is destroyed and it's still thumping around without motive or direction, but moving nonetheless. But a Romulan Star Empire without Romulus itself would be unacceptable from at least a military point-of-view, and they'd pull out all the stops to defend the planet. Therefore, if Verithrax were so equipped, she would probably have been ordered to defend Romulus, or at least Borg targets in Romulan space.
(4) Finally, if no other great power in the Alpha and Beta Quadrants used some kind of metaweapon, the Romulans' use of metaweapons would lead to some very serious questions at the end of it all. Granted, everyone was in for the fight of their lives, but if you're fighting a conventional war and some third party decides to go nuclear, well, that third party's gonna get grilled pretty severely when it's all said and done. A "balance of terror" works only if there's a balance. If one side has metaweapons, I don't believe that another side would allow that imbalance to remain unaddressed... and I don't believe the Klingons would allow the Romulans to possess metaweapons, even if the Federation did. Raid on Osirak, anyone?