You are right about the group insurance. It sits on top of the provincial coverage and is an add on to what the province offers. Your spouse can't benefit from the group insurance without first qualifying for the provincial coverage.
There are in fact private travel insurance policies that will cover some of the costs related to giving birth but these policies must be purchased before someone is pregnant. So moot point in this situation.
Yeah, there is at least 6 or 10 waiting period before being pregnant. Plus such insurances do not come cheap.