PTI is up to the discretion of the prosecutor. If said prosecutor is building a political portfolio, the chances of being given PTI in NJ are virtually zero, barring extraordinary countervailing influences coming to bear. Virtually all NJ prosecutors are building such portfolios. It's what they do over there. I must therefore conclude that the prosecutor in question must have been leaned upon with some less-than-subtle force.
If you are fortunate to get PTI and you keep your nose clean for a year, meaning NO contact with the law... not even a parking ticket, the charges are then DISMISSED. That way, there was never any crime, no trial, and no conviction of which to speak.
The problem, however, is that the NICS arrest record remains. At least, that was the case 20 years ago and I seriously doubt NJ legislators, guardians of human rights that they are, would have passed anything to improve upon that reality.
The ONLY good thing in NJ criminal law is that you are able to COMPLETELY expunge a record with 10 years of good behavior after lapse of sentence. What this means is that you can stand before a judge and under oath tell him that you have never been convicted of a felony without fear of contradiction in the records. As far as the state is concerned, upon expungement, the crime never happened.
Naturally, "elements" in the NJ legislature have been trying to dismantle the expungement provisions in their law for many years. In fact, by now they may even have succeeded for all I know.
NJ is a horrible place to live. Absolutely atrocious, though it still takes a back seat to dumps like MA, IL, NY, and CA. That, of course, is splitting the splits of splits of splits of hairs.