Depends on the unit you are posted to.
If you are posted to CCOs as driver you usually have quite a high
chance of going on short overseas stint.
Long term Overseas driver is a posting. meaning you will be posted
to that Oversea camp rather than be posted to a local unit first.
Usually you have to go thru selection and interview.
For CCOs, if you are in a CCO where the camps' unit are training
school... you will have a very high chance to go since those
training school will get driver from the CCO.
If you are unit driver, then you only go when the unit goes. But if
you are a tonner driver, chances are you wun drive because SAF uses
that country's tonner driver.