GSM/Cell monitoring

I don't really know where to fit this topic but:

Does anybody know what criteria is used to find the serving/dedicated cell on a cell phone when there is NO SIM CARD inserted? Is it the strongest signal, the closest signal, what could it be?

In my siemens module I use at^moni command...

[307 byte] By [murilo.pollaa] at [2007-11-27 8:31:48]