Yes, the changes apply on all road types unless there is a median dividing barrier between you and the emergency service or roadside assistance vehicle.
The changes apply differently depending on the speed zones:
On roads with a speed limit up to and including 80km/h
On roads with a speed limit up to and including 80km/h, you must always slow down to 40km/h when passing a stationary or slow-moving emergency service or roadside assistance vehicle with flashing lights or a siren.
On roads with a speed limit over 80km/h
On roads with a speed limit over 80km/h, you must slow down to 40km/h when passing a stationary or slow-moving emergency service or roadside assistance vehicle with flashing lights or a siren if it is safe to do so. If it is unsafe to slow down to 40km/h, you must simply slow down as safely as possible.