There are lots of UFs that aren't in first person. Harry Connolly's Twenty Palaces series, Thomas Sniegoski's Remy Chandler series, the Skinners series by Marcus Pelegrimas are some I can think of off the top of my head.
The defining features of UF isn't the POV-that's rarely something that defines any genre/subgenre. Mostly it's more the content, and with UF it's a very much debated thing of what it is.
Harry Connolly's Twenty Palaces series is most definitely in first person.
I agree that urban fantasy does not have to be in first person.
I don't know how to multi-quote, but your comment on Charles de Lint had me intrigued. I thought for sure Emma Bull's "The War of the Oaks" preceded his work, but it does not. De Lint's "Moonheart" came out 3 years before.
CS Lewis' "That Hideous Strength" might technically be urban fantasy, since the bad scientists are working for demonic entities, but most don't think of the work as such.
Charles Williams (a not so famous Inkling) wrote what look like urban fantasies, but I have not read them. I heard they were difficult to get into.
HP Lovecraft would technically be urban fantasy, but usually is considered horror. Or maybe his own special category - Lovecraftian (which the Twenty Palace series sort of belongs too, also).
The urban fantasy Dracula is technically a epistolary novel, composed of newspaper clippings, diary entries, letters and so forth. (Hmm, I seem to have almost exactly quoted the Wikipedia entry by accident.)
Maybe I'm thread hijacking, sorry.