Yes, Dependents are permitted to work in Canada. They need to have an Open Work Permit for this. It will allow them to work full-time anywhere any Canada without any curbs. They can reside and work in any part of the nation excluding Quebec.
The only way to obtain this Permit is after arrival in Canada. They must then obtain their Work or Study Visa at the earliest. The sponsor can file for their Open work Permit only if they have a valid Canada Visa.