No, calling 911 as your rescue plan is not considered to be an "on-site rescue procedure" which can be "ready for immediate implementation" for the purpose of rescuing a worker from a confined space. Emergency services do not replace the requirement for on-site rescue procedures.
Employers remain solely responsible for ensuring that there are adequate on-site rescue procedures that are ready for immediate implementation in order to effectively remove a worker who has been overcome in a confined space.
Section 11 - Confined Spaces Regulation (O. Reg. 632/05)
Consuming recreational cannabis in the workplace remains illegal after legalization on October 17, 2018. Medical cannabis is subject to different rules than recreational cannabis. The production and sale of medical cannabis is regulated exclusively by the federal government.http://www.ontario.ca/page/cannabis-legalization