Selection of clearance
To clarify the selection of clearances (at least in Melbourne) the clearance selected is based on the departure runway and arrival runway in use. For example while Melbourne is on runway 16 arrivals 27 departures all jets requiring 16 will be issued a BISON SID. If we are 16 only they get the standard (DOSEL/NONIX etc).
If this goes wrong and it is not picked up along the way then a departure from 16 will unexpectedly turn across the 27 departure path. In other words this one wrong clearance can cause a BOS pretty much on its own.
To suggest that the clearances are computer generated overstates what is actually done.
Blue