Yes it is, atleast most of them.
Just copy the files from the IT folders that the, object/particle it requires, for example.
An object like a tree needs the .mesh file which is the tree itself, the .material file, and a texture/image.
However, copy the files the object needs. Paste it into the "My_Objects" folder.
Then you'd have to load the object from within the "Object maker" in FH by writing the name of the object/particle.
Example of this is Superdupertree.mesh and then press "add new".
Save it to a group, and then you can use it in the map maker.
Just make sure you don't put 2 copies of something, and check so you don't put a particle in the FH game folder that already exists, if you do, it might give you an ogre error.