Last I knew a guristas hideaway does not escalate to a scout outpost. A hidden hideway can but a hideaway should only escalate to a ded 3 (guerrilla grounds).
Btw this is not the best way to do outposts if you want to do them. The only good thing about this system is you get the complex to yourself. But if I was serious about doing outposts, I would find many more and quicker by just scanning for them.