It was not delegated to anyone in my department. It was done under the authority of the president of CBSA and CBSA as an institution, which is a direct report to the Minister of Public Safety. The Department of Public Safety's role, and my role, was to participate in the discussions that went on around managing the border. That is how I am aware of the ArriveCAN app.
On November 17th, 2022. See this statement in context.