AFAIK, scanner data still cannot be used for discipline due to inaccuracy and unreliability (that is, they can
try to discipline you using it, but they will lose the grievance), so as
@psd181 points out, unless the supervisor actually witnessed the event, they won't prevail with discipline.
Regarding whether or not the scanner knows if you're driving or walking--it determines that by how fast it's moving, etc. So theoretically, it "knows" if you're walking or driving, but, again, unreliable/inaccurate. There are all sorts of ways to screw with the information the scanner collects, which you can find out by Googling . . .