Since they do it for Wishes, I assume they do it for Hallowishes. We heard all the P&P fireworks music from the beach at the Poly and the concierge lounge.
You get a great view from the Poly beach as well, and that's a lot easier to coordinate schedule wise than 'Ohana. I think Hallowishes is usually shown at 9:30 during the parties, which is pretty late for dinner.