There are no map connections in the 4th generation, because all the maps are 25x25 blocks, they all are made just in one location of the map. So for instance, if you were creating a town or something in that particular area of the world map, you'd have to put the objects in that particular map, but as for the special maps, they just need to be made, it doesn't require you to have to just put the objects in a certain map layout. But what I do know... is that if you go outside to the right of a special map, it brings you right onto the normal maps that are all based off the location of the town map.
In the 5th generation however, I've noticed that all the maps are consisted of special maps, so there's no maps that rely the location of the town map, this is pretty much why it's all adjusted so that the player cannot go outside the boundries of the maps. And yeah, there's no map connections in generation 5th either.
So yeah, no matter even if a map is blank... you can always change it from a no-go map to an actual map with objects on it. But remember, the mystery zone maps in the 4th generation consist of one texture object, as for the 5th generation has null maps that have one object on them, and where ever there is no map data, you cannot be able to enter that area. Except in the 4th generation, the blank maps are still mystery zone maps.