If you add custom curves to the animation, you can make a float parameter with the same name in your Animator Controller and Unity will automatically update it every frame with the value of that curve so you can get it from there.
But I have no idea if that technique can be used for curves that are already controlling something.
What I try to achieve is to correct offset values for specific bones when I apply animations to specific characters. You know, sometimes limbs don’t have the exact appropiate angle and such and is really bothering.
Can be fixed manually but is such a waste of time.
I made some google searches I found ideas similar to yours in old posts, but still, I couldn’t came up with a straight solution.