Assuming this study is valid (see below) I would think that in the case of heavy drinkers versus abstainers I think it's more a matter of what you end up dying from and how long it takes to kill you. Perhaps those who abstain tend to be more prone to stress related ailments and that comes on quicker and tend to kill faster than diseases associated with heavy alcohol consumption i.e. liver cirrhosis, kidney disease, etc.
Note, the study also claims that those who tend to be moderate in their alcohol consumption tend to live longer.
BUT Before I believe the results of this (or any other study) I would need to see details regarding exactly how the data sets were obtained, how they were compared, and how the final expectations were computed. I have seen all too many studies (done by experts) which were wrong because the researchers made a certain assumption(s) that were not mathematically valid. I have seen this happen not once but MANY times, in studies done by persons who should have known better. I suspect the samme may be afoot here.
So, until I see the details I remain skeptical of this study, as I would be of any study.