It's all of that. When we hire someone, we test the employee. Therefore, we know what this employee's language skills are from the very beginning. The person either meets language requirements or not, and then moves on to the next stage. Throughout an employee's career, they are regularly tested on their second official language. If those skills have become weaker, the employee will take a course. Often, employees will take courses on a regular basis. Many of them do this simply to maintain their language skills.
On April 13th, 2010. See this statement in context.