What happens, when extending the edge pixels (at the Edge menu of the automatic lense correction) is applied to a camera RAW file in Photoshop CS6? Does Photoshop add additional pixels from the camera´s sensor array which possibly are part of the RAW file but are not visible in the (preview) image or does it just extrapolate pixels up to the original pixel dimensions of the image?
Automatic Lens Correction can be done in ACR or Using Adobe Filter Lens Correction. I don't think using both would be beneficial. You seem to be referring the Adobe Lens Correction filter where there is a pull down for Auto Scale Image Edge: pull down Edge Extension. Since this is in the Filter Lens Correction plug-in it working with a Pixels in a Photoshop Layer not a RAW file or even an embedded RAW file in a smart object layer therefore there is no sensor RAW data available.
Using Zoom and Preview in Both ACR Lens Correction and the Filter Lens correction to me it looks like the image push outward be more like a crop
Well, on this page it is written at "Automatically correct image perspective and lens flaws > Search Criteria" that "By default, profiles based on image sensor size appear first." I guess this is a reasonable argument to assume that the extended edge pixels at the edge menu - in order to fill blank areas from e.g. pincussion distortion - are taken from the image sensor. When shooting images in RAW, I choose a certain number of pixels for image width and height. However, the image sensor seems to acquire more pixels (which are not visible in the RAW file image area by default as they are beyond the chosen image size/format of the RAW file).