Hi, I am too interested. In my case, we have one project file with about 200 animations. Sometimes I (as a programmer) would like to tweak some small changes, but I have to go to the animation guy and tell him. And now there is also audio guy adding keys for sounds. I didn't find ideal workflow - right now we just need to tell each other who is working on the project and the others are blocked. But since spine project is only one file, I can't see much space for collaboration on one project. It could work with a file for every skeleton setup and every animation (similarly to Unity animations, where animator and animations are separated files), but I suppose that this might not be possible.
Another option is to copy the specific animations over to some master project. I am still thinking about it, but I think that would need some more complex command line tools, like import etc. so I can make some tool to bulk manipulate the project file (doing that manually from menu seems too clumsy to me). I see that manipulating the project file directly is not possible as it is in some proprietary format.