I'm sure most of them were hired. To an extent these people would have replaced those leaving due to national attrition (pensioners, mainly), in part they're not necessarily dedicated to film finishing, some of them would fill positions that technically were required for years but there were no financial means to fill them, and to an extent they would have to play a role in meeting the demand of film that has grown in recent years. So a bit of everything, most likely.
PS I expect most were not specifically need for film finishing.
PS I expect most were not specifically need for film finishing.