I can see that the topic is hot, so I conclude what some colleagues have already said here. A clone of the card can be made, but only with cards from the 128COMPV1 - COMPV2 algo, supposedly from theory it is possible and there is a special programmer for this, but only in theory - the reader costs over a thousand zlotys and trying to read V2 cards, unfortunately, is related to damage as in V3 . Maybe in V2 it is not related to the algo and pulling KI for the card (IMSI is not a problem as you know) but the main thing is that V2 has been added for a long time (if not from the beginning) a new security has been added, which can be called Card Limit - when trying brute force, and all copiers are based on this, the card at 5/10 thousand attempts simply stops responding and is dead ..... for information I will mention that for the USB reader the time to reach 5/10 thousand attempts to "knock" KI is some 2 -3 hours ....
So if someone has a card issued before 2001, he can clone it without any problems ..... it is not possible for two cards to log into the network for a longer period. After logging in and IMSI replica in the BTS network to which the second phone got, it turns off - it is related to the generally known encryption in GSM (RAND / A5 etc.)
When it comes to sneaking, firstly it's illegal and secondly, it does not involve a copy of any card - the device is called Spyphone ... and it is simply 2-in-1, i.e. added modulators, end and card, i.e. 2 phones in one ... someone it is the phone from which it is calling the selected phone number and someone hears what this person is saying ... it's such an exclusive bug, but it is independent of the distance, because it is already handled by BTS