While they're in service, they receive all their regular salary, etc., so they don't need disability insurance. But once they're released, once they're transferred, if they have to be medically released because the severity of their illness precludes their ongoing service, then it becomes the responsibility of both Veterans Affairs Canada with their programs to look after them as well as SISIP.
Evidence of meeting #19 for National Defence in the 41st Parliament, 2nd session. (The original version is on Parliament’s site, as are the minutes.) The winning word was care.
A recording is available from Parliament.