What is the ruling on eating meat available in Canadian markets given the difficulty of easily obtaining halal meat, and is it permissible to eat chicken in restaurants of unknown source or to eat from the People of the Book meat that is not halal?

It is not permissible to buy or eat meat that is known to be non-halal (definition), and invoking the name of Allah (Tasmiyah) does not make permissible the consumption of meat slaughtered in a way that is not prescribed by Sharia (definition). Tasmiyah when eating is beneficial in cases where the manner of slaughter is unknown, provided the slaughterer was a Muslim or a person of the Book who slaughtered according to Sharia. The proof for this is what Aisha, may Allah be pleased with her, narrated that the Prophet, peace and blessings be upon him, said to a people who asked him about meat of which they did not know whether the name of Allah had been mentioned over it or not: "Mention the name of Allah and eat it." Everything found in Muslim markets and what has been slaughtered by Muslim Bedouins is presumed to be permissible.