Thanks friends.
I could see this on the website that we need to look for National Safety Mark label attached to the seat. This label indicates that the seat complies with Canadian regulations and standards and is legal for use in Canada.
Every child car seat and booster seat sold in Canada has an expiry or useful life date on it and should not be used past that date.
http://www.mto.gov.on.ca/english/safety/choose-car-seat.shtml
However, I was wondering if there were separate rules documented for visitors at all, as in general. I read in other forums where parents of small kids have been discussing about preparations to be done before travelling to another country, and most suggested to carry own car seat as the safest option, as the car seats provided by taxi/rental car companies either are not in good condition, not clean, torn up, expired, or not provided at all. Is every parent with a child visitor to Canada expected to buy a baby car seat approved by Canada regulations even if travelling for a smaller duration like a week, and planning to use taxi/rental cars.