Here are the eligibility rules for health care coverage in BC.
MSP - Eligibility and Enrolment
I don't see any mention of health status and given the provisions of the Canada Health Act I would be surprised to do so.
Canada Health Act - Wikipedia, the free encyclopedia
Basically you, as a Canadian citizen, would be eligible for coverage three months after your return to Canada. Your DW, who is not a Canadian citizen, would need proof of legitimate residence before applying for health care. Speaking from personal experience, this does not require her to be a landed immigrant, but she needs to be in the country legitimately. I was covered for several years after I first arrived in Canada based on a work permit. You will be able to sponsor DW for permanent residency. As you can see from the below link, the sponsorship application will proceed faster if she is outside the country.
The health assessment that Keith refers to is an immigration physical with associated tests. I had to have one during the application process for landed immigrant status. Any abnormalities found on the assessment will have to be followed up before the physician can submit the final report. Immigration Canada can deny landed immigrant status on the basis of an adverse health assessment, or may require that a treatable condition be addressed before signing off on it.
Note that once you and DW have your BC health cards, you can keep your coverage while out of Canada for up to 7 months in a calendar year. However, long absences would likely jeopardize an application for landed immigrant status or citizenship, and should be deferred until it has been obtained. This may be moot if you complete the sponsorship process for DW before she moves to Canada.
I hope that's helpful!