Frustration of Employment Contract Can be Plead by the Employee or the Employer :

In Hockstra v Rehability Occupational Therapy ( 2019 ONSC 562) Justice Mitchell had a case where the plaintiff had been off on disability for 8 years and had no hope of returning to work. This judgement confirmed that the doctrine of frustration is a matter of law, thus either party can claim that the employment contract has been frustrated.
In most cases the employer wants to rely on frustration, as under the common law, no notice is required. However in this case the plaintiff wanted to rely on the doctrine because upon a finding of frustration he was entitled to both termination and severance pay under the Employment Standards Act of Ontario.