The max zoom level in WvW (FOV-at max etc) allows y to look over walls in some cases and to place fields inside towers. Yeah, a lot of people are using that zoom-out mod which is illegal (according to the user agreement) but who cares? (Anet does not :D)
Its also still possible to bug in the SW Tower (green and blue border) for a thief and port the rest in. Not to mention EBG there y can bug in the green keep(direct inner), Aldon, Anza and blue keep (first outer than inner). On desert y can bug in Fire (inner) and air (outer).
All this is known for years and still not fixed.