Snowfalcon,
The geostationary point in the Sputnik case was the observation point on the ground. In this case, it's whatever observation birds picked up the transmissions, be they sat datalink or otherwise (radalt, weather radar etc)
Go into the login pages of your aero-I or aero-h system and most have Doppler listed.
Doppler analysis (analysis of the signal frequency and it's shift) doesn't need a continuous login, it needs the same ping to be sampled by 2 separate satellites, whether they are national assets or part of the satcom network, matters not a jot.
http://en.wikipedia.org/wiki/Transit_(satellite)