CRA (the Canadian tax department) has issued a statement allowing an employee to attend an employer provided party that is generally available to all employees as long as the cost is reasonable (up to $100 per person is their guideline) without having to report a taxable benefit for Canadian income tax purposes.
"This article provides information of a general nature only. It is only current at the posting date. It is not updated and it may no longer be current. It does not provide legal advice nor can it or should it be relied upon. All tax situations are specific to their facts and will differ from the situations in the articles. If you have specific legal questions you should consult a lawyer."