That would be an extremely weak passive signal, if it gives one off at all, which I seriously doubt. Quite a few of our smart munitions utilize the L1 and sometimes the L2 bandwidth for GPS aquisition to trim their inertial instruments. Using your logic, the would be very suceptible to be homed in on by defensive measures and that is simply not a concern. The only thing our GPS systems have to worry about is being jammed by blankets of energy beamed in the general vacinity at the bandwidth of the GPS band the munition is using....and there are counter measures for that.
I find it very unlikely a passive GPS system can be tracked. Sorry.
Believe as you wish, no need to apologize. If its electronic, it gives off a tell tale signal that can be tracked, specifically.