They would use cctv images to trace those journeys.
Wigs. Baseball or other headwear. Dyed hair. Glasses etc
Searching for male? Or female?
Which transport would they elect to scrutinise ? Which routes would they elect to scrutinise ? Why would they elect to pore over public-transport cctv looking for --- whom? On which days/or nights ?
I don't think the journeys would be neccessary. Phone triangulation, I believe works on the phone towers trangulating on the phone signal.
ETA Ignore this, misread original post