Of course they caught 450 peaks. Each passby of any motor vehicle will generate a peak.
That system/deployment is much better than noise snare (trying to capture from above instead of horizontally, deployed in an isolated area instead of the city) however it's still no bueno. Trucks would show up as incredibly loud as the distance to the mics will be something like 25% of the distance of a smaller vehicle. Based on how the array looks, my guess is the ring of three mics is used to beamform and trigger a measurement when the source is directly under the center measurement mic. Again, it could be influenced by other noise sources (or a reflection from another vehicle). You should be able to pick out gross offenders, but any exceedance less than 5 above the guideline can probably be beat in court.