Do you have the Fate System Toolkit?
It has a rather evocation-esque magic system called Stormcalling in it. And a bunch of other, more thaumaturgy-like, systems too.
That aside, you might be able to port over DFRPG spellcasting more or less unchanged if you also port over the other Powers. The systems are really very similar, apart from DFRPG's heavy focus on Powers.
The main sticking point is that Core compressed the skill list. Maybe Will could take the place of Conviction, while a magic-specific skill called Spellcasting could do Discipline's job. Might pick up some parts of DFRPG's Lore, too.
