The LegacyMIDICCOutEvent includes the field 'sampleOffset' as do note on/off events. MIDI CC's are sample-accurate. It is therefore possible to synchronize the timing of MIDI CC events with note events (which are also sample-accurate).it is not clear whether timing information is included in that legacy out function. And they are on a separate queue from notes, as per the above, so synchronization between notes and CC's cannot be absolutely guaranteed at a fine level.
However, VST3 has no concept of 'order' between events that fall on the same timestamp. i.e. it is not meaningful to say that one CC happened 'before' or 'after' another CC with the same timestamp. They happen at the same time.