+1!
Love the variety, both in the visuals, the layout and the required approach. Plus, the nice thing about it is - since the bases are so obviously hand-crafted to the location; they can't copy 'n' paste this engineer base to other locations. Each one will have to be unique, surely.
Hmm - I suspect they are PG, it's just that someone has likely increased the rules by which they are placed. It would be interesting to hear an answer from the devs.