I can’t cite sources, but AFAIK mesirah applies even if the party is guilty. However, it is sometimes muttar (obviously, AYLOR) when beis din is not an option. This might be such a case.
I don’t think they give tickets for car alarms (although they might technically be able to, I don’t know for sure).
I also can’t imagine (again, sorry, no source) that one can’t do teshuva on this.
Wolf, you are usually an advocate of AYLOR; could you please let us know what he says?