Celerity and interactions with out of combat movespeed.

I'm going to provide an example to ask my question more clearly;

If you had mobi boots on say a Janna and because of the bonus Out of Combat Movespeed from the boot, you got extra AP for celerity. Would that bonus AP be applied to a dmg based spell like Zephyr, even though it takes you out of combat. I remember a dev stream and they were talking about mobi boots interaction with Hecarim passive and how it doesn't give any extra AD, even on the first hit.