I am a little unsure of your situation. I take it that you are facing this time if and when you are sentenced. Unless the jail sentence was stayed for appeal or some other reason you could not have been sentenced as yet. Case law allows a Court to give you credit for rehab done before your sentence. However, the Judge doesn't have to give you this credit. So you either have to get assurances from the judge or wait. That should be part of the sentencing negotiations with your attorney. If you wait, unless a bed is ready on the day of the sentence, the Court will most likely sentence you to jail and allow for the rehab after the jail sentence or when a bed becomes available. Case law indicates work release is not available but try anyway. The rehab time will reduce your sentence day for day. If you do this up front you will have 90 days remaining. I am not totally sure of the rest of this answer. You must serve 60 days (less time served, but not the rehab time) prior to being eligible for parole and there are notification requirements for the prosecutor that could mess this up for you."Good time" and "work" credits are available on a Municipal Court county jail sentence. The GT and W credits could reduce down the remaining 30 days if you are not released on your parole eligibility date. However, the case law is that GT and W credits do not reduce a minimum mandatory sentence. Unlike other MV statutes the DWI title says 180 days not "up to" 180 days. I should know the answer to your question but I can only advise from experience, I cannot find any case law directly on point. All courts I have seen figure the 90 rehab and then 90 jail. I have had some courts mandate 90 jail and others assume that only 2/3 (60) would be served. I know this is little help. Call my office and I'll find out definitely from Corrections. 908-687-6650
If this is for a DWI (third offense or greater), then you must serve the entire 180 days, of which you can have a credit for up to 90 days for each day spent in an inpatient treatment center approved by the IDRC. You will have to do the initial 90 days first and then the inpatient treatment. Further, if you do not do 90 days you will have to finish your time in the county jail.
There is no work release or good time credits if you are serving a 180 sentence for DWI. You must serve day for day time.
Assuming this is the sentence for a 3rd or subsequent conviction for NJ DWI, you must serve the entire 180 days in the county jail. You can get up to 90 days credit off the 180 days if you spend such 90 days in an IDRC approved inpatient rehab facility. The 90 days rehab stay is supposed to follow the initial 90 days in jail.
Under the case of State v. Luthe, 180 days in jail means jail. You cannot satisfy the 180 days jail sentence with alternative sentences of house arrest, community service, SLAP, or ankle bracelet/wristlet. 180 days jail means 180 days of straight jail time. The 90 days of inpatient rehab is your only jail alternative.