i believe that it says in agreements that they cannot buy any shares but i may be wrong, look up in spsa.
the other thing to do would be to say all of fnma, fnmas, fnmat, fmckj, fmcc etc etc are all same and thus wash rule would kick in. many are harvesting tax losses. irs should care about it as it lost revenue and such a rule is in power of the powerful people. they are missing out on loot going on by large funds. lol.