Regardless of where your corporate headquarters are, employees and employers need to comply with the jurisdictional legislation where the work is being done. This is especially concerning in the current work environments post-COVID with digital nomads and telecommuting. Unfortunately, many governments have not caught up to this new workplace normal. Fortunately, there is not as much variance across provinces in Canada as you might think. In response to your specific question about human rights and harassment: in a digital work environment, the courts prescribe to the fact that the jurisdiction where the complainant is working is the presiding jurisdiction. Specifically, if you have an employee in BC that was harassed online by an employee/manager in Ontario, the employee would file the complaint with the BC Human Rights Tribunal and your company would need to respond in that jurisdiction.
It would, however, be a good idea for you to have a harassment policy for your organization that is written to the highest jurisdictional standard to make sure you are protected across the board. The good thing is that such policies are easy for you to find here on HR Insider.