Wow. I am on disability leave and my manager started trying to get rid of me a year into my leave. They finally terminated me last month, not even following the government's own directives which is to approve medical leave for two years and possibly more based on each situation. They would have dumped me months earlier if I had not requested union involvement. My rep told me that my department does this all the time. He advised me to file a human rights complaint for discrimination (disability) and filed a grievance but not much is really going to come out of it. And I no longer have a job to go back to. Really cruel stuff.
I would assume it depends on your department. I hope you have a more supportive employer than I did.