Quote - Could this have been implemented using Maya muscle, trying to figure out how the wrinkles where achieved. Edit - ok it mentions wrinkle maps so guess not (no idea what a wrinkle map is)

I don't know about Maya specifically, but in 3dsmax, it's done simply through parameter wiring.  In Poser language, the action is similar to a JCM.  You can use any translation or object parameter to drive the adjustment or changes of another parameter automatically.  For example, you can have two distinct bump maps... one for a "relaxed" face, the other containing specific wrinkles.  Using a special blend material, you can "wire" any action in the scene, such as the rotation of a bone, to drive the parameter of the blend material, and blend between the two maps seemlessly.  Almost any action in the software can be used to drive any other action.  Same principal is at work in Maya.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.