I replayed Enemy Within over Christmas and can tell you that when you see them in the hanger view, your regular interceptors are referred to as Raven 1, Raven 2, etc. Firestorms get the more concerning Demon 1, Demon 2 call signs.

From this, I guess we can assume that Voodoo 3 is the designation Central gives to units in the air at any given time, regardless of their official designation?