The answer is I am not sure, it is complex and I will investigate. Let me explain a bit.
First, it is hunting season right now. So I am sure that is why you saw them.
Second, hunting is not allowed in the regional forests, so if they were in the forest part of the trails that would be an issue.
Now, for the Hydro Easement itself things gets complex.
There is a gun club near the Hydrocut. I do not know if it would be allowed for them to walk from the gun club to a place along the Hydro Easement where they are allowed to hunt just carrying guns and not actually hunting. I am looking into this.
Also, the land of the Hydro Easement is not all owned by the Region, so depending on where exactly you saw these hunters it may have actually been on private land where they could have permission to hunt — or they could be illegally on the land without permission. Is it possible for you to be very specific about where they were?