Re: (Major Spoilers) How Come WE've Debated Just about Everything But.
Nope, it's military-grade retrofitted Borg tech, curtesy of the Tal Shiar.
I think the Narada being based or using Borg tech makes perfect sense, it is a powerful ship, and the Borg have always proven to have some of the most advanced technology out there, it would make sense to use it to build a powerful ship. At the time he comes from there are Borg parts that have been salvaged from all the interaction with the Borg. It was even mentioned in a Voyager ep that there were Borg cubes in the Beta quadrant, and if Nero is from the Beta quadrant, perhaps has run into the Borg at some point.
Nope, it's military-grade retrofitted Borg tech, curtesy of the Tal Shiar.