Brendan,
There are a good number of studies out of Texas A & M regarding feral bee populations, but they all cover areas in Texas. The latest study covering my area was done in 2005. The results are pretty irrefutable, since they used mtDNA analysis to identify the matrilines of the bees. Samples from aerial pitfall traps indicated that about 40% of the bee population are of AHB matrilines and the rest were divided between the Egyptian honey bee and EHB. So indications are that a pretty large percentage of feral bees are of AHB origin.
There is no doubt the their presence is on the rise here in Texas. We have had at least 4 stinging incidents this year with at least two fatalities that I can recall. So I would not count on the 18 deaths in the last 20 years statistic holding as their presence continues to escalate.
All that being said, I would agree that there is a considerable amount of media hype associated with the AHB and that they are not quite the "monsters" that the media and others would have us believe. After all, the beekeepers in S. Africa keep them and manage them in much the same way as we do the EHB. However, the stinging incidents in S. Africa are probably not covered nearly as widely if at all so I don't know how valid that comparison would be.
I do feral cutouts in my area and keep the colonies, but I also have them tested for their mtDNA source and any that are AHB matrilines are either re-queened or destroyed. Research seems to indicate that colonies that are headed by an AHB matriline queen are much more likely to develop the super aggressiveness when their daughters are mated to AHB drones (as would very likely happen during supercedure), so the best defense is to make sure that your colonies are headed by EHB matriline queens and keeping lots of drone comb in them so that you flood the drone pool with EHB drones. Vigilance in keeping track of your queens is paramount, since if a few AHB queens slip in, those colonies will start kicking out lots of AHB drones. By the time one of them is superceded and becomes aggressive, you have already seriously contaminated your drone pool. This certainly does add to the overhead of keeping bees in AHB territory.
I don't know if this helps you much, but I would not get too gung-ho about keeping AHB. The facts are out there that they can and will attack more readily and in greater numbers than EHB. As their prevalence becomes more dominant, the stinging incidents will continue to increase. Just by keeping EHB in AHB territory, you will not be able to keep their genetics out of your stock. I would take a lesson from the beekeepers in Mexico and points south. They have found that by using EHB breeder queens to generate the open mated daughter queens to head their hives, they can manage bees in AHB dominate territory. Is it more work, yes for sure. But it is probably the only approach that is going give the public much confidence that AHB are manageable. Also I don't know about in your state, but here in Texas it is still against the law to knowingly keep AHB in managed hives. At some point in time, that will probably have to change since the AHB genetic material will eventually creep into most Southern/SW US beekeeping operations regardless of our efforts. But at this point, I think an attitude of "since it is inevitable, I might as well embrace AHB now" would not be well received and could land one in a good bit of "hot water" legalwise if you know what I mean.