There is a database of every players previous teams that feeds into a formula that provide a teams initial ranking. Organizations can also offer their input for out of norm circumstances. The placements are then fine-tuned with placement games, and then appeal games in some cases. In general I think PAHL does a nice job with placements.
I agree with others that these teams will almost always have a team in every AA division:
Allegheny
SCIR
North Pittsburgh
Foxes
Lebo
South Pittsburgh
*SHAHA
*Predators
*SHAHA and Preds to a lesser extent, because they sometimes try and force AAA teams upon certain age groups, which tends to dilute their PAHL teams. Their AA teams are oftentimes borderline A Major/AA type of teams.