With a good and accurate depth map obtaining a high-quality stereo pair is not a difficult task, especially if you have a clean plate up your sleeve. Problems usually begin when boundaries of objects in the depth map are not perfectly matched to original image objects. In this case simple stereo generators will produce artifacts and excessive stretch-like effects in stereo. However, correction of depth maps and suppression of such artifacts are still possible to do automatically in a stereo rendering software. Here is a stereo sample made with YUVsoft Stereo Generator. The depth map for the video was quite rough, though the final stereo looks pretty good after the usage of additional options for depth map correction.

Source image and rough depth map

Cropped stereo mate, general mode

Cropped stereo mate, advanced options used
The software enables occlusion output so it’s not a problem to use clean plates and externally restored background and merge layers directly without any additional mask.

Cropped stereo mate, advanced options+restored background used
You can find more information here:
http://www.yuvsoft.com