An application to the board based on a Form N12 – Notice to Terminate Tenancy for Personal Use may not be successful since Unit B is available to you. As per the legislative a landlord can offer the tenant the alternative unit to reside in, instead of paying the tenant one month’s compensation.

Interpretation Guideline #12 deals only with the eviction for own use situation, for example, it explains the test to be met is that the landlord must require the unit in good faith, which is closer to “wanting” than “needing” the unit in the eyes of both the Board and the Divisional Court.  https://tribunalsontario.ca/documents/ltb/Interpretation%20Guidelines/12%20-%20Eviction%20for%20Personal%20Use_dec2020.html is where you will find more information on how the Member usually looks at these situations.