I can't speak to the aberrant tactics of individual elders but:
When you switch congregations they send:
Your publisher's cards (I think officially they keep 8 years) which contains your name, address, phone number, whether you are a regular pioneer, MS, elder, other sheep (OS) or anointed, male or female, plus the numbers you turned in to them month by month, year by year.
They will send a cover letter as to your spiritual "health" in the congregation.
If you are currently on restrictions, they should mention that.
The WTS has said too that someone who was dealt with judicially as a pedophile is supposed to be identified as such (not accused only if they were actually DF'd (reinstated) or reproved (publicly or privately). I know that a few elder bodies have done this...have all?
A lot of unofficial information passes between elders over the phone that may never be in that letter but will nonetheless impact on your future in that new congregation.
Any judicial action paperwork in the old congregation remains in the old congregation. They are not supposed to pass it on. If you were DF'd and started attending a new congregation, your request to be reinstated has to go through the old congregation who will advise the new elder body based on any new information they provide.
Elders have a hard enough time doing the paperwork they are assigned to do, let alone making up folders on each JW in the congregation. Most rely on word of mouth. No paper trail and if the facts get muddled, no problem.
Blondie