I looked at render / nurb's tessellation and I will need to research it further but it seems to be tided to the a small subset of the tessellation attributes of all nurb's surfaces (curvature, u,v division factor, smooth edge and edge swap).

But it's kind of clunky and requires you once again have to tinker with all the tessellation options above in the maya tessellation section of the nurbs attributes on a surface by surface basis.

It does not create a node so you have to set it on a object by object basis. It does not appear to show in the attribute spread sheet which would be nice.

It only applies to nurbs although quick inspection seems to indicate there is an equivalent poly based attribute under polyshape node / tessellation attributes has a "use max edge length" but I am not clear how that would be tided to render camera.

I will certainly experiment with them though just so I understand better how they work in the avent I have to render using maya software, but I think the mental ray approximation node system is more flexible as it can be applied to nurbs, polys, subd's, smoothed, unsmoothed+displacement.

I am glad you pointed it out though as maya is loaded with stuff that can easily get missed and I like to understand all the features and tools.