Dunno if they are randomized, but for me they were in the sawmill just south of keytones position

They are, every computer terminal has a random chance. Every time you die or load an old save it changes.

dunno for you guys but i got it after i raided the main radar station and basically razed it. it was a document (meaning it's an item you got to have space for, yeah)
do pay attention to the dialogue, as you are told when the mission is given that the plans can be found in the more important CSAT base(s)

Yeah they were south of keystone for me after i reloaded, thanks for the help.