Like I say it all depends on the configuration of the system. Someone else noticed that his rang (from the caller's perspective) even when he had the phone shut off but I would have thought that by shutting off the phone would have deregistered and there would be no "ringing". However, deregistration is a one-attempt and no retries thing and so is not full-proof.
full-proof = fool-proof (I guess)
So the bottom line is that the ringing MAY OR MAY NOT be important...and you cant just automatically say that the caller will hear ringing if the SIM card has been destroyed at the bottom of the ocean or by explosion.