The ACA sites are not "public land", they are private property to which public access has been granted. In AB, there are two basic types of public land - forest lands (in the aforementioned Green Zone) and Crown Lease - lands that are owned by the province, but are not public access - you need to get permission from the leaseholder. Most lease lands, even the ones that allow public access, do not allow camping, etc., at least without explicit permission.
The Green Zone is generally open public access, though some areas are closed to motor vehicle access, and camping is allowed.