Apparently Southwest requires what's called a G30 release. I'm told this isn't normal since the fares are still filed in the regular public tariff, but they're doing it nonetheless. So as of now, the only distribution systems that have access are Sabre and Galileo while the others do not. Oddly enough, any airline that requested to see Southwest's fares back when they started filing them was granted access by Southwest as well. Maybe that was a condition of allowing them to be restricted from some distribution systems.
Thanks, Rick, for the additional info.