peliosisYou are confusing filtering and partitioning. Octrees/grids/kd-trees, etc are only a method for spatial subdivision to accelerate data lookup (or reduce memory when looking up data from a file). Such a data-structure may be extended to contain for each node some information about it's child nodes (average values, sum, etc) - such a structure is “filtered”, e.g. renderman's brickmap.
Octree is a mipmapped structure for efficiently wrangle pointclouds, and prman has it for a couple of years now.
For example: 3Delights/PRman point couds are tiled (don't know if they use a grid or octree exactly), but they are not filtered - each node contains just the points. Brickmaps are pre-filtered - once the octree is created, starting from the leafs an average of their values is computed, all the way up to the top (root) node - just like a texture mipmap.