For a few years, I was an unwilling landlord for a property down in Florida, which I contracted with a property manager to handle on my behalf.
As part of that arrangement, they drafted the lease, which included a clause to permit entry by the landlord, which stated:
Landlord and Agents shall have the right at all reasonable times, and by all reasonable means, given reasonable notice, during the term of this Lease and any renewal thereof to enter the Premises for the following purposes...
I've omitted the listed reasons, but they relate to things inspections of the property, repairs, efforts to sell the property, and to leave notices. Failure by the tenant to permit these inspections render the tenant to be in default.
Note, that there are no specific time tables provided, in part because there are many things that warrant inspection on short notice. For example, if a pipe breaks, we need to be able to enter the property immediately. However, for most anything else, we would notice via e-mail or phone call 48 hours in advance. Presuming an amiable relationship, the tenant could shift this timetable, however, the right to inspect the property was always important.
To address your specific question, "If a landlord enters residential premises without receiving a judgement for possession and without the presence of a Special Civil Part Officer what recourse does the tenant have (in NJ)?"
I'm not sure for NJ, however, for Florida it's doubtful we could be charged with trespass. We have a right to be on the property pursuant to the lease. We could not change the locks without notifying the tenant without a court order, however, we could change the locks pursuant to the terms of the lease; for example we'd need to give the tenant a copy of the new key, however, if the tenant is non-responsive to notices they might not be able to claim their new key.
Bear in mind, there are multiple other elements in the lease which can give rise to justify an inspection by the landlord in an eviction proceeding including, but not limited to: affirming status of the unit at any point during the eviction process (if you damage it, we will want that damage included in the judgement), ensuring that standard maintenance is occurring (we don't want the unit to become someone's personal landfill), ensuring that the property is not abandoned (a common occurrence in an eviction), ensuring that the property isn't being subletted (another common occurrence in an eviction).
Literally every single thing I listed in the above paragraph occurred during an eviction I had on the property. For those reasons, we want to be able to access the property. And if the property manager I hired is to be believed, it's legal for us to access at any time pursuant to the lease they drafted.
For the record, I had little interest in pestering my tenant provided the rent was paid on time. The only times we'd enter the unit during normal circumstances were for maintenance and once a year to conduct an inspection. Things are notably different if we've elected to resort to eviction.