It depends on the circumstances when they leave the pension plan. As I just explained, if employees were to leave with a vested interest—for example, they had 15 years of service and they decided to take a deferred annuity, so they've left an interest in the old plan—and they were to come back as employees, they would come under the old provisions of a retirement age of 60. If they had no ties to the current pension plan and they came back again after 2013, they would be subject to a retirement age of 65.
On November 5th, 2012. See this statement in context.