Jjajaj it is available in Clarisse, Vray and Arnold but only for Alshaders in Maya.
This is weird because Arnold does not support it, but the Alshader does??
So I guess that maybe there is some coding reacquired on a shader level.
But honestly, it should be implemented in any render engine by now. The fact that it saves a lot of work and time, especially for compositing.
And that is why Vray is promoting this feature so much, because right now they are the only ones who really support it.