While XIV BP's exist in the code, it is set not to drop. Sorry
Not even Hegemony has the blueprints or facilities to build new XIV hulls. (At least according to the lore)
This of course is not true.
During a raid, there is a chance for "Burst" of blueprints to drop. You could potentially get approximately up to 5 rare blueprints in a raid.
After repeated 25 raids on that 8 population hegemony planet I've attempted(so I could rightfully appropriate their nanoforge), I hit jackpot and stole their XIV blueprints with blueprint burst.
I am only using a faction mod, graphicslib, magiclib and lazylib so I am pretty sure this is intended behaviour.
Edit: In addition I've scoured about 70% of the uncharted sector. I have never ever seen XIV blueprints drop from there.