可以 it is not required by law to have a car seat in a taxi, but it is recommended that the customer provides his/her own.
Taxi drivers are responsible for ensuring that passengers under the age of 16 are wearing seat belts. The law does not require the taxi driver to provide a child car seat. When travelling in a taxi with a child, you may provide your own child car seat or booster seat.
http://www.mto.gov.on.ca/english/safety/seatbelt.shtml
What are the seat belt and child car seat requirements when I am a passenger in a taxi?
There are no seat belt exemptions for passengers in taxis—only for the driver when carrying passengers for hire. A passenger must use his/her seat belt.
Taxi drivers are exempt from the child car seat and booster seat requirements when transporting a passenger for hire. However, taxicab drivers transporting children for personal reasons or those that operate a taxi while under contract with a school board or other authority for the transportation of children are required to comply with the child car seat and booster seat requirements.
If you are 16 years of age or older, you can be charged for not wearing a seat belt and face a fine of $240 if convicted. If you are under the age of 16, the taxi driver is responsible for ensuring you use the seat belt properly. Taxi drivers who fail to ensure children are using a seat belt properly can be charged, and if convicted, face a fine of $240 and two demerit points on their driver record.
http://www.mto.gov.on.ca/english/faq/safety.shtml#exemptions6
出租车公司貌似没有出租座椅的业务
I'm visiting Ontario for three months and will be renting a car during my stay. What will be the new rules for transporting my children?
Exemptions from the child car seat requirements are no longer available for vehicles rented in Ontario. All children who should be in a child car seat or booster based on age, height and/or weight must be properly secured in the appropriate child restraint system.
If the vehicle is rented outside of Ontario, all infants (children under nine kg) and toddlers (children who weigh nine kg or more but less than 18 kg) must be in a child car seat.
If you are travelling with a child who should be in a booster seat, and the vehicle you are driving is registered in another jurisdiction, then you are exempt from using that booster seat for the first 30 days of your visit. After that period, your child must be in a booster seat. This exemption will be completely removed on July 1, 2014.
http://www.mto.gov.on.ca/english/faq/safety.shtml#exemptions6