I think the OLC press release answers some of the above questions. Operationally it is a licensing of DCL. Paying for the ship, Management and
operations are in fact being handled by OLC.
Though the OLC presser specifically goes on about Disney Cruises, a reflection of the current fleet and essentially the product that is a Disney Cruise. So I don't think an integrated booking relationship is entirely ruled out, nor do I think it is strong, either.
But it would be in both companies interest to have an integrated relationship, I'd imagine. Though quite tricky, because it is a licensed partnership and not a stake of DCL. I think the best solution would be to both run their own separate booking portals and software, but having some kick-back integration in booking abilities. And reciprocity in Castaway Club? But still staying arms length.
They are also spending 2 billion on this... but I must say there may be cruise terminal, booking, staffing costs rather than a flat 2 billion on just the ship. Hard to say what the breakdown is.