ExMo and Pegasus,
Excellent question! The service actually has multiple methods of issuing the best fare. The specialized agents are extremely familiar with all of the ticketing rules, exceptions regarding country of origin pricing depending on type of ticket, and also work with agencies in several low cost countries to search out the best fare based upon your needs. But you simply deal with one agent for all changes, modifications, etc.
It provides you a single contact point that you can use on a regular basis. I encourage you to try it out for a quote and see how well it works. Then let me know what you think!
The service also has very good access to other carriers as well should you choose to go non-Oneworld for a particular segment or trip.
Cheers!