I'd like to apply the same cutting operation this does on Mesh A onto Mesh B but can't extract the cutting planes or refer to them. They're tangled up into feedback loops and compiled blocks. Do someone have any tricks on how to get them out intact without affecting the rest?

Unfortunately the cutting planes get generated recursively from the previously cut pieces, as such, in order to extract them you'd still need to perform the cuts and store the cutting planes at each step, making sure to separate them out before processing each piece again.

Since they encompass each piece with some extra padding to ensure the cuts go through the whole way, you'd then need to cut your Mesh B recursively by each generated cutting plane in the same order they were generated in the first place - you wouldn't be able to simply gather all cutting planes and cut in one go unless you boolean union the lot and go through and painstakingly cleanup all the protruding faces to ensure no partial cuts.

If your Mesh B bounds differ from the bounds of Mesh A, the cutting planes might not extend far enough to generate clean complete cuts in the first place.

maybe you can fracture a box big enough to contain either of the meshes

and then for each of the fractured box pieces intersect with MeshA, MeshB, MeshC, ... to get similar piece cut out of any of those
so in theory you will get them cut the same way
havent tried, just an idea

In the first output of the RBD Material Fracture node, you can blast the groups labeled "*inside" and use Delete Non Selected. This gives you the inside faces of all the pieces which coincides with the cutting planes.