I am an NJ attorney currently working with about 15 applicants throughout the state and having helped many more in the past. In my experience a decision within 30 days is the rare exception. There are a few unreported decisions from both the law division (superior court) and appellate division that have interpreted the 30 day limit to apply "unless good cause for denial exists" Now we just need a court to limit "good cause for denial" to the limited exceptions of N.J.S.A. 2C:58-3.
Back to the OP question, I've found that a letter on my firm letterhead addressed to a township/city attorney can sometimes speed up the process. The township attorney doesn't want a lawsuit against the town and will sometimes nudge the PD a bit. On the other hand, it would take a deep-pocketed client to front the thousands needed to bring a good case based on the delay and the city attorneys know that. Overall, enforcing the time limit has no easy answer in my opinion.