We’ve received this response from Niagara Glen park staff, in response to a question about Niagara Glen parking.
Every annual parking pass, including the one that comes with the Bouldering Permit, purchased for the Niagara Glen can have up to 2 license plates from the same household. These however, cannot be purchased at the machines, as they only accept the one plate. Individuals can buy the annual parking passes for 2 plates at the Butterfly Parking Booth with one of the attendants or from the Falls Parking office. Also note, since the change to the policy that permits up to 2 plates was only introduced on Jan 1, 2017, annual parking passes purchased prior to this policy change would only be eligible for the 1 licence plate.[If you have] a valid bouldering permit from October 2016, [your] bouldering permit is still valid. By presenting this bouldering permit at the Butterfly Conservatory, [you] should [receive] a parking pass valid until the current bouldering permit expires.