I wouldn't discount the possibility of a clever Lawyer convincing a Judge his client should get the 20'.
The vacated land has to vest back to the lands it came from. If the court, judge, commission, council or whatever political body gives additional land to the attorney's client it would be repugnant to the constitution... an illegal taking of the land of others without compensation.
The Government can effect a taking without compensation. Usually it's inadvertent or an accident. The property owner can bring an action in inverse condemnation within the statute of limitations demanding either return of the taken land or compensation but they can't force the government or other taker (such as a utility or railroad) to return the land. As soon as the statute runs in the absence of a lawsuit the taking is complete, the record owner can't recover the land or gain compensation. Our courts have ruled this is not a constitutional violation, I forget the exact reasoning.
The clever lawyer I mentioned above would argue that the centerline of the 40 foot R/W is the boundary, there is no transfer of land either way, so no taking of any kind. This is strictly hypothetical of course. Naturally the other side would have an expert who would successfully explain that the boundary is at the original platted centerline and the Judge of course would adopt that theory of the case, naturally.