For some reason, the Gates of Arah have become always accessible, at least on my server, Whiteside Ridge. Regardless of whether we currently have control of Shank Anchorage or the Gates themselves, the Gates of Arah waypoint is permanently available, and so is access to the dungeon. I am assuming this is a bug, and therefore reporting it to ArenaNet.
Gates of Arah always accessible
Actually this is intended. It was in some patch notes that the dungeon is now accessible most of the time. Basically there was QQ that it was always closed because some thought the events were too hard to open it and thus some servers would rarely do them. It will become contested when he final event (defeat the high wizard) of the chain is active, or when he defend event happens