Full interception and not 'only' the collection of metadata is possible. IMSI catchers can also be used to block mobile phone usage in an area or send SMS to us

Full interception and not 'only' the collection of metadata is possible. IMSI catchers can also be used to block mobile phone usage in an area or send SMS to users in an area (for example to participants in a demonstrations, already done in the Ukraine). Without full interception, a hidden ID check is IMHO a good analogy: Instead of stopping all persons in an area in order to ask them for their IDs, you collect meta data on all mobile phones and use these data to identify the persons in the area.