"Or is that only an outbound route from Archerfield??"
No, it is two way, but there is high terrain at the eastern end near Fernvale to Lake Manchester and as you turn to the southwest for Archerfield. Flying that route requires a healthy respect for terrain clearance. If the weather was as poor as reported it would have been a difficult route to negotiate.
Getting a clearance is only an issue when the military have hardware airborne. Generally, they are quite accommodating.