Using CVOpenGLTextureCache in Plugin on OSX - Get correct OpenGL context?

Has anybody had any luck getting CVOpenGLTextureCache working in a Native plugin on OSX? I have the code working outside of Unity fine - but I can't seem to get it to work inside of Unity. I think the issue is that I don't have the correct OpenGL context - CGLGetCurrentContext() doesn't seem to return the correct one.

I I think thats whats going wrong anyway - as soon as I try to use a texture created from the cache with Texture2D.CreateExternalTexture unity locks up.