If your filepool policies A, B, C are path-based, you can use
isi filepool apply --path=/isi/path-for-A --recurse
In more recent versions of OneFS, there is also the more efficient SmartPoolsTree job type available in the job engine.
However, if your filepool policies are based on other criteria, such as file sizes of time stamps, I'm not aware of any automated way native to OneFS. Of course, you could use a standard UNIX "find" with parameters mimicking the filepool criteria in question, followed by a plain (non-recursive) "isi filepool apply" on the matching files.
hth
-- Peter