This is a really gray area. Disney doesn't want you to use outside photographers. Yet, guests are allowed to bring cameras, of course. And Disney can't prove that someone was hired or just a friend, although they may get suspicious if a photographer is shooting a wedding every week and saying they are just a friend. Even then, with the vast number of cast members and different locations, you are unlikely to run into any trouble.
The best way to go about it is this: Don't lie. Actually become friends with your photographer. Have him or her structure their contract so that they are just technically shooting your getting ready/off property shots. Then, once the in-park stuff begins, they will attend as your guest and friend of yours.
They will bring their camera as a guest, but they will not be technically getting paid for this time. They're just helping you out. (Of course, they can WAY raise the price for the getting ready session to insure that they are getting paid fairly, or they could sell you an album afterwards, etc). That way, if approached, they can say honestly that this is an unpaid shoot and they are just a guest.
It is done all the time. People opt not to have the Disney photographers because they have a friend or family member who will do it. Same thing here.
If you want to be doubly sure, the photog can bring a copy of the contract and their invitation. They should also check to see what equipment is allowed to be brought in.
In today's world, guests have very nice cameras. It is really, really hard to make the determination between guest and pro photog, especially for a CM who doesn't know much about the different camera brands and lenses.
