For testing purposes in #0007526 i added a single line of [USE_EVIL_ANIMALS] to the dwarven entity and am sharing my results.

Trolls brought along on embark are simultaneous 'other animals' and untrained peasants (easily seen by how the starting 7 population is now 13 with 6 extra trolls brought on embark) none of the trolls are livestock or war trainable by default of not possessing tags like [PET] or [TRAINABLE_WAR] any way even though use_evil_animals treats them when placed in non-controllable civilizations and impacts the game buggily when they are added to a playable civilization. Comparably #0010613 can be used for reference here for how unmanageable creatures happen to break the game if they aren't properly able to be realized through real creature tags that define them.

Oddities include site overpopulation in regards to high amounts of beak dogs & trolls attributed to [USE_EVIL_ANIMALS] allocation over regular animals, and a buggy interaction with trolls being half-citizens that need feeding which the game does not seem prepared for, best seen in the populations of the fortress of Ushrirlames, "Quakeround" with 239 dwarves living there and 52 trolls & beak dogs (suspiciously equal amount, since they are the only ones influenced by use_evil_animals) tying back into overpopulation of sites #0007526 way above the normal or capped amount in only 30 years of gameplay.

World was generated in a otherwise vanilla dfhack folder which shouldn't effect anything.