My son born in canada, want to apply "right of land" to HK, can he interview in toronto?

Do you mean your son want to apply for HK permanent Identity Card? The application can be dropped into Chinese consulate in Toronto, and it will be sent to HK for processing. For more information on this, you can check http://www.gov.hk/en/residents/immigration/idcard/hkic/oappic.htm