Question on this "a job with extended health care benefits won't be of any help in terms of covering your child's care before your child qualifies for provincial coverage". How does it work for visitors on work visas? Won't companies provide extended health care insurance for their employees and their dependents? If I am able to secure a job that provides medical insurance, won't my child be fully covered even is he has no provincial coverage?
No - that's not how it works for work permit holders.
Temporary work permit holder qualify for provincial health care coverage and this extends to any dependent children (i.e. the dependent chidren receive provincial health care coverage as well). The employer benefits would then sit on top of that. This would be after any waiting period (e.g. three months in Ontario).
Again, the employer benefits do not replace provincial coverage - they supplement it (i.e. cover things that the provincial health care coverage doesn't). This is why it's almost always requirement for beneficiaries to have provincial health care coverage in order to qualify for the company benefits. I went through this with my own husband when I sponsored him for PR. He could not benefit from the additional coverage provided by my company until he had PR.