What is the situation with QF and pre-boarding?

Since the demise of AN I have done a bit more QF domestic travelling (about 20 or so flights in 02), and pre-boarding seems very inconsistent.

Sometimes, there is a call for business & OW emer/saph. But other times, it is just a general call.

Is there a policy on this?

What would make sense is that when the flight is full, they have pre-boarding, and when it is say <75% full, they just have a general call.

However, I have found no pre-boarding on full cityflyer flights on a number of occassions, which doesn't fit this policy.

Mmm.... Interesting (for some I guess)...

MD