http://en.m.wikipedia.org/wiki/Mobile_phone_tracking#section_1
Not sure if this will help, but it explains how mobile phone's are traced. I'm currently very curious as to how they traced her phone and what actually happened with it and the sim card etc.
The technology of locating is based on measuring power levels and antenna patterns and uses the concept that a powered mobile phone always communicates wirelessly with one of the closest base stations, so knowledge of the location of the base station implies the cell phone is nearby.
Advanced systems determine the sector in which the mobile phone resides and roughly estimate also the distance to the base station. Further approximation can be done by interpolating signals between adjacent antenna towers. Qualified services may achieve a precision of down to 50 meters[citation needed] in urban areas where mobile traffic and density of antenna towers (base stations) is sufficiently high. Rural and desolate areas may see miles between base stations and therefore determine locations less precisely.
GSM localization is the use of multilateration to determine the location of GSM mobile phones, or dedicated trackers,[3][4] usually with the intent to locate the user.[2]
Localization-Based Systems can be broadly divided into:
Network-based
Handset-based
SIM-based
Hybrid
Network-based
This section does not cite any references or sources. (October 2011)
Network-based techniques utilize the service provider's network infrastructure to identify the location of the handset. The advantage of network-based techniques (from a mobile operator's point of view) is that they can be implemented non-intrusively, without affecting the handsets.
The accuracy of network-based techniques varies, with cell identification as the least accurate and triangulation as moderately accurate, and newer "Forward Link" timing methods as the most accurate. The accuracy of network-based techniques is both dependent on the concentration of base station cells, with urban environments achieving the highest possible accuracy, and the implementation of the most current timing methods.
One of the key challenges of network-based techniques is the requirement to work closely with the service provider, as it entails the installation of hardware and software within the operator's infrastructure. Often, a legislative framework, such as E911, would need to be in place to compel the cooperation of the service provider as well as to safeguard the privacy of the information.
Handset-based
Handset-based technology requires the installation of client software on the handset to determine its location. This technique determines the location of the handset by computing its location by cell identification, signal strengths of the home and neighboring cells, which is continuously sent to the carrier. In addition, if the handset is also equipped with GPS then significantly more precise location information is then sent from the handset to the carrier.
The key disadvantage of this technique (from mobile operator's point of view) is the necessity of installing software on the handset. It requires the active cooperation of the mobile subscriber as well as software that must be able to handle the different operating systems of the handsets. Typically, smartphones, such as one based on Symbian, Windows Mobile, Windows Phone, BlackBerry OS, iPhone, or Android, would be able to run such software.
SIM-based
Using the SIM in GSM and UMTS handsets, it is possible to obtain raw radio measurements from the handset.[5][6] The measurements that are available can include the serving Cell ID, round trip time and signal strength. The type of information obtained via the SIM can differ from what is available from the handset. For example, it may not be possible to obtain any raw measurements from the handset directly, yet still obtain measurements via the SIM.
