Sure, Disney routinely rents out their parks for corporate evening events, and - in theory - to anyone else with pockets deep enough.
I once got to enjoy Hollywood Studios while attending a business convention with my husband. After the park was closed to the public, all us conventioneers were bussed into a back entrance. The restaurants were open and serving complimentary food, there were food carts also - no charge for those Mickey bars!, Tower of Terror, the Rock and Roller Coaster and Toy Story Mania were all running, cms were holding dance parties, there was even a special fireworks show for us!
The year previously, this same group had booked Islands of Adventure to do Harry Potter after hours, and the year before that they booked the Magic Kingdom.
(Ah, the good old days, before budget cutbacks meant no more fancy conventions!)