Having a hired photog in-park isn't allowed for Memories, Wishes, or Escape. What *is* allowed is an outside photog in other areas, and then attending the guest as a reception, unpaid. Disney doesn't restrict the lens length or amount of equipment a guest can bring in, and if you are truly not being paid but taking photos, then they have a hard time restricting that.
Additionally, I have assisted at Disney as an outside photog for conventions and know they escort outside photogs into the park for those events (Living Seas Salon in 2010, I can't remember where this year). And this was allowed for this event.
Lastly, I'm fairly sure Couture collections are allowed outside photographers-that's been a rumor around town for awhile. This wedding looks in that price range to me. Some people spending $100k or more on a wedding may not be satisfied with Disney's quality, and Disney itself may not be able to offer what those clients want. Spending 100k or more would probably necessitate a custom contract and not a package deal such as with Escape, Wishes, etc, so open to more negotiation about outside vendors. Correct me if I'm wrong, but I'm thought the Arndts have shot couture weddings in-park.