Borg Solo Armadas are now a new mechanic within STFC, in combination with the Command Center. These work similar to the Dominion Solo Armadas (Jem'Hadar Flagship).
Be sure to start the Borg research first in the Combat Research Tree. This research turns faction ships into ViDars against the Spheres. Don't bother with ViDars on these targets, as they are not strong enough.
The Borg Spheres have a massive amount of Mitigation, so the best way to fight them is a lot of Mitigation on our own ships, as well as critical hits. This way the ships last long enough to finish the fight and get the loot.
