Ok, heres a link to a panel of HIV medical experts who met recently in san fran to discuss this same topic - the possibility of transmitting HIV via receptive oral sex (ie. Woman giving man a BBBJ) .. they discussed two different scenarios - BBBJ without CIM and BBBJ with CIM. Their consensus:

* BBBJ without ejaculation can still potentially transmit HIV (through pre-cum), although it is rare for this to happen

* the spread of HIV via BBBJ with CIM is a medical reality. This happens (although lower likelihood of infection compared to vaginal or anal) - all panelists referred to cases where HIV had been acquired this way.

http://hivinsite.ucsf.edu/insite?page=pr-rr-05