Ideally they'd want to start all 16 in February but can't. They don't have enough classroom trainers, trains or driver coaches to facilitate 16, it's a struggle with 8 at times.
There will probably be at least 1 school planned for 2019 as well. Driver numbers are dwindling and have the potential to cause problems due to a shortage. There are drivers retiring, some semi retired/part time drivers who can go whenever they want, drivers taking up other roles within metro. Then there are plenty moving onto other tocs/focs, some having just left, many more just waiting on start dates and masses having interviews and assessments etc.