</font><font color="blue" class="small">( the former owner of both properties should be called upon to have the discrepancy regarding the sewer pipe documented. It seems to me that something was overlooked here, )</font>
That's my take on the history. There is no easement, because the former owner owned both properties, didn't need an easement, and probably didn't know where the property line was, anyway.
You and your neighbor both may have recourse against him.
</font><font color="blue" class="small">( talk with your real-estate lawyer only. do not talk to the neighbor, this can escalate to something fuzzy and unfriendly. figure out what you need to do to make it right, then have the lawyer make the statement, stay detached from the situation! )</font>
Good advice. My attorney once told me, "If you need to do anything unpleasant, blame it on me. I get paid for that, and they already hate me anyway. Don't you get personally involved." I had a couple of f(r)iends who had sued each other several times, and retained no animosity. The winner bought dinner. <Shrug>
It looks like there are a few things that need to be checked out and documented.
Where is the property line, the nearby buildings, the encroaching sewers, the encroaching road/parking, any ancillary damage like removed trees if it can be established in the field, and the locations of all recorded easements. Your surveyor can draw up a plat showing all this. It will be a valuable document.
What are the local regulations regarding setbacks of buildings, sewers, etc? The gummint may be your ally, here.
What was the previous owner’s responsibility in all this?
Then you can decide what you want to do, and how to go about it. You may have some options. It may be possible to have them remove the encroaching construction or abandon the encroaching sewer. If the construction is old enough, possibly just pre-dating the sale in this case, it may be grandfathered in. In that case, someone needs to pay you for the loss of value; maybe the seller. You should also, in that case, grant the neighbor as limited an easement as your lawyer can make work, record it at the courthouse, and enforce it.
It may be possible and desirable to grant them only a temporary easement, giving them a certain amount of time to remove their encroachments. That easement still has cash value to you, but it gives all parties a certain amount of flexibility. It may also be possible to tie any necessary temporary easements to the life of the improvements. IOW, they could keep their sewer, but they can’t fix it or replace it if it goes bad.
I concur with the recommendation of fencing the property line, and maintaining strict surveillance on it.