And "workshop"? What are those? Can players buy their own systems?
Private Ownership I've always been a bit uncertain about. I heard rumour it's the government applied to systems when it's a non-typical faction owning it (such as Pilot's Federation) which happens during FD-led events and stuff, but I've got no evidence of that.[1]
Workshop is the government type Engineers have. Since they can't own systems, you'll never see it.
[1] Although, EDDB might have the answer...
Minor Faction FleetCarrier in Elite: Dangerous
eddb.io
Looks like "FleetCarrier" is a faux faction which all fleet carriers are owned by. (probably because all assets must have a faction owning them, even FCs)