Hmmm... how to make sense of this question...
I'm guessing that you're referring to the "Add results of geoprocessing operations to the display" that is a check box on the Geoprocessing Options dialog box. There is no comparable setting in the "Map Document Properties" dialog box that I can see. Furthermore, "Geoprocesing Options" are not a property of a map document (.mxd), but are application/user settings. (I can demonstrate this to myself by using 2 separate .mxd documents (map documents) and turning off "Add results of geoprocessing..." while in one map document, closing that map document (without saving), opening a different .mxd and seeing that the geoprocessing option is now turned off; and likewise for turning it on.)
Our default installation is that "Add results of geoprocessing..." is turned on for every user/machine installation. And, it would surprise me *very* much if our users were sophisticated enough to go fiddling with the Geoprocessing Options. Turning that off or on is completely unnecessary for our workflow.
Notwithstanding, I did check my 10.2 installation (where I developed the Python script) and I checked the user's 10.1 installation (where the script was used) and both had "Add results of geoprocessing ...." checked on.
And, just in case you think to ask, the python script does not make any reference to the arcpy.env.addOutputsToMap setting (i.e. it neither reads it nor sets it).