In my case, I was initially released in 2014, on a voluntary basis. After two years, in 2016, they told me that I was being released for medical reasons. At that time, I learned through newsletters, documents or newspapers that I was eligible to apply and that I had a set number of months to activate my priority status in the public service.
Evidence of meeting #171 for Government Operations and Estimates in the 42nd Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was military.
A recording is available from Parliament.