User blog comment:B214/Chapter 474 ranting/@comment-25111584-20160222140821/@comment-25111584-20160222155500

Actually, Aquarius telling Lucy that her key has been respawned was just a bonus. She could as well have come before it had been respawned. The key had no connection with her return. She used the CSK's power to return.

And we'll definitely get some sort of explanation regarding Ultear. Whether that is to your (or my) liking waits to be seen.