It would be easier if you can post a still and be more specific on what kind of effect you are looking to apply. I can think of a way to do this but only for certain kinds of effects. Post some more details.
Most gladly, picture below. I've got this thing growing out of the corner and I need it to split perspectives growing downward. I can do this by masking the comp in halves and ball-parking perspective, but...this project is going to have me do this probably at least half a dozen times.
Was wondering if there was a plugin or some solution available that can help distort a basic line for this application.
If you're referring to the shadow branches/roots, I would pre-comp the animation, make it 3d and change the anchor point to have the Y axis at the point where you want the bend to be, duplicate and rotate one of the layers to match perspective. Link one layer to the other and use the latter to position both. This way you have one animation/effect that can be adjusted in the pre-comp and the ability to position and match perspective.
Another way would be to use Free Form or FreeForm Pro to bend a layer in 3d space and match the walls.
Actually, also an added step that would really help as well would be to...
After setting the anchor point like you mentioned use a basic triangle or square primitive to represent angles of the effects shape/object you want to use and then once the angles are flush turn on desired effects layers.
That way you can have a more true "faux" relationship of angles.