What are the rules/laws in Canada that prevent discrimination against HIV/AIDS patients in the workplace?
Canada is different from the United States in the application of laws that protect HIV/AIDS patients in the workplace.
While in the United States federal law is used to regulate just about every case of HIV/AIDS discrimination in the workplace, in Canada the rules are shared by, both, the Canadian federal law and by the provincial or territorial governments. This means that Canadian provinces and territories can add to the general Canadian law based on the unique needs of the territory.
The Canadian government's federal law protects HIV/AIDS patients in the workplace through the Canadian Human Rights Act, whose commission includes AIDS and HIV patients' rights.
The territorial and provincial governments, however, vary their laws and regulations. For example, some provinces generally apply the Human Rights, Citizenship and Multiculturalism Act, and the Human Rights Code as their foundations to prevent discrimination or the refusal of basic rights and services to ALL citizens alike.
However, some other territories specifically refer to HIV/AIDS patients such as New Brunswick's adoption of the "General Criteria for the Investigation of Complaints of HIV/AIDS Discrimination" addendum to their Human Rights commission. A similar case happened in Manitoba, where a specific mandate is worded in a fact sheet that reads:
Prohibiting Discrimination Based on AIDS/HIV Infection.
The Ontario Human Rights Commission has also adopted a specific policy against the discrimination of HIV/AIDS patients. The rest of the provinces either appeal to the previously-mentioned Acts, as well as to the Charter of Human Rights and Freedoms (Québec) to ensure that no workplace discrimination takes place, as well as to safeguard the basic rights and services of all citizens.
Aside from the specific inclusion of rights and laws regarding HIV/AIDS patients, we find that Canada seems to hold a strong position against the discrimination of people with disabilities, as it is. The specificity of what goes on in each province is the particular right of the government of the said territory to decide for itself.
In the "links" included with this answer you will find a well-detailed document regarding HIV/AIDS patient rights in Canada that should help you get even more information about this very important issue.