I have a pretty good idea of what they are yes, but I dont have a list or anything like that. Adding in the qmailqueue patch wont help on a PSA box, unless you also replace xinetd with tcpserver. The PG version of qmail does use tcpserver, and has the qmailqueue patch applied. However I wouldn't say its exactly compatible with PSA. Everything is in the right place, but its missing some things on the authentication side that would probably break it on a plesk box.
That being said, I originally did develop this for PSA integration, and there is a very old version of this in the atomic-unstable channel that is more or less compatible with PSA 7.0. You might be able to update this to do what you want:
http://3es.atomicrocketturtle.com/atomi ... t/9/SRPMS/
I abandoned the design because of the tcpserver requirement, and eventually went with what is in PG today.