Back in 10th, core rules had quick-read bullet points, one of which included "Cannot put fortifications into strategic reserves."
With the 11th core rules out, this isn't the case any more, which means hypercrypt legion is technically able to up-down some Starstelles baby!
Or even up-down the back-on-the-menu 180pt Tomb Citadel if you clear out a quarter of the board :P
(This is likely not rules-as-intended and should probably be a house-rule if used. Cheers.)
(And also on a more realistic but equally not-serious note found when searching the doc for the word fortifications, Night Scythe lost aircraft and has OC 0 rather than OC "-", so it can have OC 1 near a CCB and perform actions,