I have tried to create a FP obejct on a displaced surface. I have used the Effects tab, and added a "Follow Displaced surface (Corona)" effect. I have added the displacement map, and linked the Min/Max values with the corresponding controllers.
However, it only works for bitmaps it seems. I use a 3dsmax Noise map for the displacement, and no matter what I try, it will not line up. I tried using WorldXYZ on the noise coordinates, as well as Local, but it makes no difference.
It does SOMETHING - it moves the scattered objects to approximately the correct height - it's just that the noise doesn't line up.
Hope there is a solution for this, since I use noise maps a lot.
Attached two renders of the underside of the displaced mesh, where you can see the objects aligning (using a bitmap) and NOT aligning (using 3dsmax noise).