Does anybody have any reference on how an areas aura interacts with enchanted items? Can an item function in a Divine Aura without penetration? What happens to a magic items penetration score in an Aura?
The penetration is affected by the aura in much the same way as a creature's is. You might decide that an item reduced to negative penetration by an aura wouldn't function, but there's nothing supporting it in the RAW. In fact, that's one of the advantages of magic items over DIY spellcasting.
Ot does not say in the RAW explictly how enchanted items use penetration, other than items have a penetration ofzero unless otherwise modified, but all effects that require penetration (like creature and character powers) follow the common addition or subtraction of aura from penetration. The rules do cover effects with negative penetration on page 82 clearly, so I would allow an item to work the same way.
When I'm making anti-fairy items (don't ask!) I try to take the aura into account aswell.
My considerations here (for stuff in items):
Fairy ward (using Rego), lvl 56 will stop a might 50 fairy even in a fairy aura up to level 6, but not higher since the level of the warding does not increase with changing auras.
Fairy oblivion (using Perdo), lvl 10, penetration 54 will penetrate a might 50 fairy even in a level 8 regio, since the penetration is boosted by 4 in a lvl 8 fairy aura (1/2 x fairy aura) while the fairies resistance is boosted by 8 => 54 + 4 = 50 + 8 => it just penetrates.
Are these considerations correct?
Yup, except that you are using a house rule for the ward: in this edition wards have to penetrate.
We do not use it in our saga since we find it rather weird (to say it mildly, compared to how some of my players have worded their thoughts on wards & penetration), but to warn you about it 
Cheers,
Xavi
So you say that officially, to stop a might 50 creature, you need a lvl 50 ward (in any aura) and a penetration of at least 50 (which is affected by aura strength, as is the resistance to this for the creature)!!!
Now I know why those lvl 50 creatures are nigh indestructable.
My first thought would also be: jikes! But perhaps it does reflect the relative strength of magic better. At least it makes al those specific wards (anti fire etc.) a lot more usefull, since they don't have to penetrate.
Noble's parma, and I may very well be wrong, but doesn't the columbae's warding ability wards regardless of penetration?
Yes, that's their advantage (which no doubt arouse from the heated discussions on that topic 
). Note; though; that it only works against beings whose MR come from Might (i.e. not True Faith, Parma Magica, etc.)
columbae? did I miss something, what are they/is that?
You can find them in HoH:S in the Ex Miscellanea. They are a group with Gaelic roots mostly found in the Stonehenge Tribunal and their strong suit is wards.
Where is the text about wards needing to penetrate?
Basic raw: All spells need to penetrate. IIRC, david chart specifically explained it also applies to wards.
Noble's parma, but I believe HoH: S also makes the point in the columbae section.
And trust me... this was a point that was beaten until the horse was not even fit to serve as a skeletal model. Even after David's answer. (I admit, I was in the "wards shouldn't need to penetrate" camp.)
it's in the berklist archives, it might be around here somewhere.
-Ben.
What Leonis/Ben said. I am in the anti-penetration camp as well (our wards do not need to penetrate, IMS). Oh the wonders of HR
Xavi