The rulebook states that “If a population center is hidden, only the owning nation may enter it . . . .” Does this mean that characters of the same nation as the hidden pop center that are in that hidden pop center hex are protected from harm by enemy characters that may also have entered that hex? - or from a curse squad parked next to that hex? In short, are your characters also considered "hidden away’ inside the hidden pop center?
Thanks.
No, your characters are not hidden away. Enemy forces can take no action to harm your hidden pop. cent. Any armies or character’s you have their are not protected by the hidden p/c.
In no pop are your characters “inside”. They’re always wandering around looking for campsites (read any/every Encounter message you’ve ever had…be they in the wilds or 2924…). There isn’t room for hidden barracks and training grounds either, so we all see the army banners.
The citizens are cowardly and hiding, which means they can’t be burned to the ground or stolen from…but then, they’re also too busy cowering in the cantina to notice/report my curse company of challenge mages either… 
What this is is trying to say is that you will not get the reports of any enemy characters in the pop center… So, if the DS send a big challenge company to the sinda capital they can do some serious damage, as they wont show on the pop report…