As a general rule there is no off-leash dogs allowed on public land, however, as a dog owner myself, I have never even heard of anyone being charged. When out on a trail most dog owners let their dogs off leash but call them back when someone approaches. There 'leash-free' areas in most towns, here are some around Muskoka:
https://www.muskokaregion.com/commun...n-bracebridge/
I avoid those designated leash free areas unless I needed to do some socialization training with the Shepherd, they are breeding grounds for diseases such as kennel cough.
For the type of training you are wanting to do, a school green space on a quiet day may be better but as said above you will run a small risk of getting a ticket.