Directly "overlapping" the material world is a portion of the Umbra known as the the Penumbra. The Penumbra mirrors physical reality, but reality as it is "supposed" to be. Though divided, the two were once joined. The spirit world still touches the material one, for were it gone completely, Earth could not sustain life.
Powerful actions on the physical plane send emanations across the spirit world. The most powerful of these psychic waves ripple past the Penumbra into the Near Umbra, where they have the potential to create whole realms. Such Realms often form based around a single idea or collection of legends. For example, the Nazi concentration camps founded throughout the course of World War II created vast hellholes with pits that lead to Malfeas or the Atrocity Realm, while the atomic bombing of Hiroshima and Nagasaki sent the psychic reflection of dead zones into the Thousand Hells of the Yama Kings.
In the Penumbra, a toxic waste dump site will swarm with malevolent Banes, while a city will be covered in the cobwebs woven by Pattern Spiders. A grove of trees will stand taller and wilder, and a volcano eruption or the flaming chimneys of factories could give birth to Fire Elementals.
The appearance of the Penumbra seems to be based partially on the viewpoint of the one bearing witness to it. Werewolves will see it in a more animistic fashion, with an immense Moon dominating the sky (the Sun, conversely, tends to be much smaller), with everything from trees and rocks to the very stars themselves being represented by a spirit. Some mages may see it more as representing ideals and concepts rather than spirits. Other mages (and the rare vampire who makes it there) will see things in a state of decay: a swollen red sun shining sickly light down on crumbling buildings and the rusting husks of cars and trucks.
An uninformed observer may assume, based on description, that there are three different Penumbrae, one for each Umbra. This is a mistaken assumption, however: if three different travellers arrive in the Penumbra, each viewing a different "facet,” they are still able to see and contact each other and interact just as easily ad they would in the physical world. Despite the varying perspectives of those who witness it, there is truly only one Penumbra.
For this reason, it is possible that the Shadowlands/Wasteland is simply one more aspect of the Penumbra.