Interesting event occurred during our last game. Two separate roads, each with a wagon. Tile placed, joined and closed two said roads. One end of road attached to unfinished, unoccupied castle. Can one/both/pecking order of which wagon can move to open castle?
Just read your post again. You said that a tile was placed that closed two seperate roads, each containing a wagon. One end of a road attached to an incomplete, unoccupied city. The question was asked as to which wagon could enter the city.
In this case only the wagon that was on the road that ended in the incomplete, unoccupied city would be able to enter, as the other road would
not end in the incomplete, unoccupied city, it would end with a now completed road (unless there was some pretty nifty tile laying involved).
In all cases though the wagon would move in accordance to the official rule posted above.