I can't speak for all of their frames, but the F5Pista framesets are made for them by Colossi. They're effectively rebranded Mondial Track frames. Not that it matters much--Colossi outsources their production frames to a factory in China as well, and only does their custom work in Italy still.

Regardless, F5 is doing some innovative stuff and deserve all the cred. The Titan stem is a pretty huge accomplishment IMO.