Yes, unless exempt.
This was the problem in this particular case. The individual had language exam results, but they were not Public Service Commission language results. They were from the other federal employer. There was confusion--there shouldn't have been, because the HR community should know this--around whether or not those results were valid.
But yes, within the public service it's quite clear: if you have a valid language result, you can be appointed. If you do not, then you need to have a valid language test before you can be appointed.