Just to clarify what a mobile phone and the mobile network can and can't do (they are my business).
Mobiles in Oz work at 900MHz and the coverage is non continuous especially in the bush.
Even when you have coverage, the only normal way that the network operator can locate you, is by identifying the base station that your mobile is talking to.
Consider that in rural areas that base station could be up to 70km away (extended cell feature in GSM) and you can see the low accuracy of any 'fix'.
If you are fortunate enough to be in a location where you can receive more than one base station, there is special software that the operator can use to try to triangulate you, however that is not running constantly and a trace has to be requested (in some countries by court order) set up and run. That is mostly used in the cases of kidnapping where they are trying to identify the location while talking to the kidnappers. Even when that system is used, the accuracy is highly variable as it relies on estimating distances, not directions, and those distances are the actual radio path from the mobile to the base station. That path may be a reflection off of a building or the side of a valley and not the straight line distance. I have worked on a software solution which attempted to triangulate users in real time and we found it was extraordinarily difficult and not nearly accurate enough to be useful.
As for the idea that the SAR plane could find your mobile, that would require that they carry a unit which simulates a GSM network and causes your mobile to try to register with the network. There are multiple reasons why that may or may not work.
The only accurate way to locate yourself with a modern mobile is by using the phone's GPS. There are applications, Apples phone finder would be an example, that use the on board GPS to locate the device. The thing about that is that you have to set it up beforehand as you must legally give your explicit permission for the network to trace you. I don't know what particular applications are available as I haven't taken the time to go looking, but the only ones which have a chance of giving your real position are the GPS ones.
Hope that helps.
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