The main findings are suggesting a slope change, which when you incorporate standard errors are just below 1 (the yellow line in the above graph). The model to me though is very noisy (should clearly have seasonal monthly terms, this should make estimates somewhat more precise), and is suggestive that the matched areas are not quite the same (they are substantively lower, although to be fair do appear to have similar seasonal patterns).
Biased because I have written a bit on this (IMO the pub health literature is biased to only conclude alcohol is bad, a similar paper saying "no effect" would be rejected at JAMA or other health journals). It is an interesting idea, I think it could probably be made stronger though (control for the same area during daytime, or a better synthetic control area). As is the 23% reduction is a bit wishful thinking I believe.