It would be obvious if they tried to get precise location (GPS) as that requires a discrete permission. However, precision location is a red herring -- it isn't

It would be obvious if they tried to get precise location (GPS) as that requires a discrete permission. However, precision location is a red herring -- it isn't needed for intelligence purposes. They are much much more interested in the social graph. From that they can likely back track to calculate approximate location (using cell positioning information and other sources). Last I looked the OpenTrace was exchanging an encrypted binary blob generated by the government, likely a unique identifier key and timestamp, which could be updated on demand by the server/app owner. Basically there is no anonymity for the user versus the Govt, only somewhat against other users.