Yes. Non-academic collaborators may be appropriate mentors for the dissertation. If they contribute substantial guidance for the project, and are well-qualified to assess the work, they could (or perhaps, should) be included on your supervisory committee. You will need to have a UBC faculty member as a supervisor or co-supervisor. Your supervisor, program director, and the G+PS Dean's office would need to approve non-academic committee members, based on an appropriate rationale.