Is it possible to have a Magical Regione inside a Faerie Aura?
Say there is a large faerie area somewhere, including perhaps a grove and a meadow. Now somewhere in the meadow could there be a Magical regio generated by an extraordinary magical event?
How about other aura/regio combinations?
Sure, why not? Whatever you want in your saga you make happen.
Imagine, for instance, that the Huntress Cult of Diana managed to find their Messiah and in so doing fulfilled their prophecy of finding and killing Quendalon in Arcadia.
The net effect could justifiably be the creation of a magic regio inside the fairy regio (Arcadia) from the epic battle.
Just one idea out of many possible. Your imagination is the limit. 
And how about other combinations, like an Infernal Regio inside a Dominion Aura, or a Dominion Regio inside a Faerie Aura? Or even a Faerie Regio inside a Magic Aura?
Noble with Headache's parma: Yes, you can. THe strongest aura subsumes the others usually, but you could have a a magic 2 aura with a small pocket inside with magic 2/4.
I seem to recall there are some exemples of this, maybe in RoP: tD, with Infernal auras subsumed by divine ones, suddenly becoming the primary aura under the right (or is is wrong?) conditions.
For a regio, you could very well have he first level being subsumed in the dominant aura, with higher levels floating above.