Unfortunately, many of these departments did not do their due diligence in drafting their uniform polices to ensure that they comply with established directions from the crown. There is nothing stopping these department and/or the provinces from establishing their own medals, as long as they are worn on the right side.
The provincial medals are somewhat confusing, as some of them have been approved for wear, and some haven't been. Ontario has a fair number that have been approved for wear, other then ones that are for criteria that is already recognized by the Exemplary Service Medals. The rule against dual recognition generally prevents these from being approved for wear. For example, Ontario has a 25-year service medal for Firefighters. This one isn't authorized for wear because that service has already been recognized. Unfortuanely, you still see many people wearing it on the left side, including a few people that I have seen wear on a military uniform.
Ontario recently introduced a Paramedic Medal for Bravery, to go along with the officially recognized equivalents for Fire and Police. Presumably, it will eventually be added to the Order of Prescidence. However, until that time, it should only be worn on the right side.