Just tested these out, here are the IDs for the online-exclusive horses:
A_C_Horse_Andalusian_Perlino
A_C_Horse_Breton_GrulloDun
A_C_Horse_Breton_MealyDappleBay
A_C_Horse_Breton_RedRoan
A_C_Horse_Breton_SealBrown
A_C_Horse_Breton_Sorrel
A_C_Horse_Breton_SteelGrey
A_C_Horse_Criollo_BayBrindle
A_C_Horse_Criollo_BayFrameOvero
A_C_Horse_Criollo_BlueRoanOvero
A_C_Horse_Criollo_Dun
A_C_Horse_Criollo_MarbleSabino
A_C_Horse_Criollo_SorrelOvero
A_C_Horse_Kladruber_Black
A_C_Horse_Kladruber_Cremello
A_C_Horse_Kladruber_DappleRoseGrey
A_C_Horse_Kladruber_Grey
A_C_Horse_Kladruber_Silver
A_C_Horse_Kladruber_White
A_C_Horse_Thoroughbred_BlackChestnut
Some notes: They'll be missing their breed name when you look at their details. Stabling them will cause them to occupy a stall and disappear. Upon reloading that stall will have a Kentucky Saddler in it. I wonder if it'd be possible to make them fully functional with a little bit of tweaking?
