This is generally what i do most. But it's been a long time since i've massively trained any particular creature for extended periods of time, GCS's were to be my next project if i could collect a massive collection of them (i'm talking having around 90+ of them).
I can confirm you can easily reach expert, but domesticated? can't remember off hand. I "seem" to remember getting wild ravens to become tame (not bred ones, but the actual wild forms, but this was with a fortress with about 200 of them, i gave the save file to someone else and they just said "what's the fascination with ravens man?!? you're freaking nuts" proceeded to butcher them all (which must have taken some time!) and gave the save back)
So i cannot confirm about domestication either way, i have reached expert in multiple occasions, but i don't believe that does the job, a legendary tamer with expert "may" be enough if done enough to a single creature, as i said, i "think" i remember taming some, but i can't guarentee anything.
This can be done with any animal whom can be trained.
I will do research, although this is likely to take a while, especially seeing i'm currently against massive hordes of undead/necromancers whom i've never really faced before and having quite a lot of "fun" and thinking about dropping them down a massive hole at the moment. But i don't like not knowing the answer to that question