I had to provide ID to Virgin Mobile before they'd even sell me a prepaid SIM card, some 6-7 years ago. Though I don't know if that was legislation or their own policy. I don't remember if Telstra required ID but I certainly had to provide details to activate.

On the other hand, in New Zealand I was able to get a Vodafone SIM card, put it in my mobile and use it right away. That may have changed by now, though I doubt it because I'm not really sure that terrorists would want to attack New Zealand anyway.

In any case, isn't it possible to get a rough location of a mobile anyway? If it's being used in a single location for long enough then it's probably enough for authorities to track down the address. Besides, terrorists (and criminals) will just resort to identity fraud, so overall it's pointless and will just mean that law abiding citizens are the ones being denied privacy/anonymity if they desire it.