User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4521561-20121224015716/@comment-3146930-20121224154801

Not really. I mean we don't exactly know how Hades' sword works. As far as we know, someone has to be physically touched by the sword in order for it to send or retrive someone from the Underworld (at least that is what the page says, as well as the Keys of Hades page). At least I believe that is how it is explained in the series. Hades may be able to call souls to him even without the sword, as he is lord of the Underworld. Annabeth and Percy aren't souls however, they are still flesh and blood and as Nico stated, not even the gods go into Tartarus.

Hades can't call them up if they aren't dead and the Keys of Hades may only be able to unlock the gates of Tartarus, which would allow any number of enemies to escape. Still not sure how Ethan managed to release Iapetus however, unless he dropped the sword into Tartarus and took it back from the Titan when he crawled back out.