hey Steve here, the BPF+ work was done mainly by Andy Begel... really good stuff but it never got incorporated into libpcap, and I never otherwise published how the original optimizer worked. I did, however, give a retrospective talk on it a couple years back at sharkfest...

http://sharkfest.wireshark.org/sharkfest.11/

Click on "Keynote Video" for a really boring talk :-)