As far as I can tell, the Copyright Act only provides for human authors. If an employee or several employees create a work in the course of their employment, do they own the copyright, so that it enters the public domain 50 years after the death of the last author? Or does their employer own it, in which case some other law applies?
Whether the employer or the employees own the work is a red herring, the term is the same: life of the author(s) plus fifty years.
If the identity of the authors are unknown, the copyright term lasts until fifty years after publication, or seventy-five years after creation, whichever comes earlier.
See the Copyright Act sections 6, 6.1, and 6.2.