I didn't ask the AC agent if they would cover overnight accommodation in Halifax, due to weather-related delays. Next time I will ask
Thank you all for sharing your experiences.
If AC refuses to pay for accommodations, due to the weather-related or other delays, I am still not sure how difficult it is to claim it from my CIBC VISA. I am reading the CIBC travel insurance/interruption insurance policy, and it does not indicate what documents are required.