This is in the US, but the US mobile phone companies are legally required to be able to track people by phone according to this article, and can not only use their masts to track you but it appears they can enable the GPS in the phone and get updates from it (although this is extrapolated from a journo's writings so probably wrong).
---------- Since 2005, US law says that mobile phone providers must be able to locate 67% of callers within 100 metres and 95% of callers within 300 meters.
This requirement has led to GPS capability in most new mobile phones in the US.
"This is very useful, although we can only use it in emergency situations such as when a person is missing or lost, or a life is in danger," said chief Anderson.
Knowing this, police officer Todd Neale contacted the mobile phone provider, AT&T, which gave him GPS coordinates every time the phone was activated. Police must submit a compliance form to the phone provider to request location information.
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Hmm, potentially scary, but useful too. Mild head-scratcher, that one.