Don't know the rules in Atlanta, but it is common, that HOV lane rules don't apply to weekends .
Again not familiar with the expressway system in Atlanta, but I've seen HOV lanes being the far left lane, with no breakdown lane available, just up against concrete barriers, and lets face it, if you had a serious problem with your vehicle, with the lack of driving etiquette these days, it's not uncommon for other drivers not to let you lane change, if you are not at least doing 20+ mph over the posted speed limit .
Not enough information available here to get a good idea what all of the circumstances were .