I will ask my dear colleague Trevor Knight who is an expert in political financing at Elections Canada to complement my answer. I would only add that the definition of candidate at the beginning of the Canada Elections Act says that a candidate is a candidate until all the financial obligations that are required under the act have been complied with.
My understanding is that at the end of this process when all financial returns have been provided and all debts have been reimbursed, the bank account should be closed and when a new campaign opens, then the new candidate should open a new bank account.