The owner of a parcel of land cannot sell more than they own or convey a better title than they currently have.
If the township nor any of the local residents have complained things probably won't change.
However you won't own the land either but just have the use of it like the current owner does.
If it's an obscure part of the township land it's possible you could buy it or acquire it from the township as surplus land but asking would call attention to the situation.
Ask a local real estate attorney what to do if you're interested in owning the land otherwise just let things go on as they have been.
There's a slight possibility the lender may require some of the fence to be relocated if you have it surveyed and the survey shows the fencing not entirely on what you're buying.