I said build not level, it only need blueprints to build at lvl 0.If you've never been plundered before and you are at least in Iron Age (the 2nd part I am not 100% sure of - maybe someone might be in EMA and never been plundered), then when you are attacked AND plundered - it triggers the quest. Otherwise you have to wait and get bps off of someone who gets it in a questline. And the gb does cost to build -- at least above level 0. It is like any other GB.
Just seems like something to satisfy plunder crybabies to me.