It is unclear which of the three towers is supposedly Wygan's broadcasting location for Radio Freeform. Harper simply describes her drive to the tower by saying: "I drove to the row of red and white broadcasting towers on top of Queen Anne Hill and parked in the small, deserted lot outside the tiny building." (Greywalker p. 258).
From her description, we know the building was "tiny", though. That description tends to indicate that the tower at 151 Galer Street is the most likely tower as it appears to have the smallest of the three buildings and also has a small lot attached to the back.