I go by the fact that anti-fighter beams damage your hull and bypass your shields completely. Do they do damage to shields in retail? I can't remember for sure. So certain shields may be merely resistant or impervious to normal weapons, but beams don't seem to apply to this restriction since they seem to completely bypass shields for smaller craft, so it makes sense for bigger beams to be able to completely bypass capship shields too, right?
Maybe the Lucifer had shields because the Shivans never expect other races to have beams like they do. It is intended to repel normal energy weapons and mass weapons, so it is still added protection from bombers and other weaponry, even if other species have beams, and it would take longer to destroy it since only beams might pierce it.
As for my assumptions in my earlier post: I go by the most likely assumption based on the story line and tech description of the Shivans and what I think makes sense. If it wasn't true, then why would Volition say 'hive' in the tech database? Just to make you wonder or just for kicks? Did it say 'could be' and then list other possibilities? The tech database said 'most likely' constructed by another entity too, and I like that idea, since it said 'most likely'. I don't think V would say it unless it had meaning to the story if it is being said in the tech database.
If they are from subspace and constructed by another entity in real space, maybe this other entity put subspace beings in machine bodies and this particular subspace (beings) are conscious, like spirits, or in scientific terms that seem close to the same thing, energy beings that can control bodies. So maybe we are fighting subspace itself but in the form of physical Shivans, 'shells' for these subspace beings that let them interact in real space in order to protect subspace from real space beings.
@Matt: In English, we also use words like 'maybe' or 'probably' or 'might' to express opinions, and I have done that in many cases throughout the board.