I wonder if the marina considered a mooring field, since they're reserving the whole bay anyway. Considered how busy Pirate's and DeCourcey Island get, I'd image there would be a demand. Not that I would personally prefer a mooring field - but if this 'private water lot' ownership allows the marina to prevent anchoring, moorings might at least reduce some of the crowding in nearby anchorages..
I doubt they'd actually relocate a vessel without notice (and if you were onboard, I'd imagine you'd be able to put up enough of a fit to prevent it). Do they have any authority to ticket/fine a boat?