The public lot is open 24/7. I see camper vans, boat rigs and sled rigs all hours of the night.
I've also seen motor homes towing various rigs stay over night. I also see day trippers parked along the entrance to the harbour.
I personally park by the public launch. The trail runs right across the parking lot. The parking lot hosts parking for the salmon derby. I've counted well over 50 rigs at once. OHL hockey nights can get busy.
Owen Sound trail from the Bayshore community centre/East side boat launch is finally open. Plenty of parking. Best Western Inn on the bay is also located right there.
Unfortunately we have no trails other than the railbed open. It's about 35kms from the trail head to the first available loop at Berkeley.