It would depend if each personality is independent in each ship or if they are connected together via the mindscape into one meta-identity.
I re-read Sourcebook 1 last night. It's still not very clear. A brief summary is here:
http://wiki.travellerrpg.com/Black_Imperium#History_.26_Background
Lucan originally uploaded "copies of his personality" to 17 of his flagships. They used a "tame" Viral Entity to control the ships under their command. That wouldn't have required a Mindscape if the ships were in the same system. They could be controlled through radio. No mention is made of controlling ships in other systems/sectors.
Operations were slowed a couple of times while the flagships argued over who was going to do what. Elsewhere it's stated that the various Lucans fought over power. Apparently, the copies all thought that they were the real Lucan.
When Lucan's health started failing, he uploaded himself to the palace computer. He overwrote the copies in his flagships. This is where it's not too clear, but each Lucan seems to believe it is the "original."
The palace computer was destroyed by the "Grand Fleet of Humaniti" in 1218, so the "original" Lucan is gone. The Grand Fleet hunted the "Lucan Ships." They thought they got them all, but they missed at least one.
The Lucan Entity on
INS Invincible commanded the "Last Stand" against the K'kree in 1247. (Avery turned and ran.) They never did find
Invincible, so it's possible that Lucan is still out there somewhere.
So, it would seem that Lucan was
not a meta-entity and a Mindscape wouldn't have necessarily been required.
OTOH, perhaps the Imperium had some sort of Top Secret Mindscape Project?