The problem will come with distributed networks on 5G. imagine you have a base station say at big ben. 100 people connect to that, then others connect to each other , you can have mobiles sending data to each other through the distributed network rather than over the telcoms providers kit.
At that point tracking mobile phones is akin to a snooker table with thousands of balls being tracked over an extra dimension of time. This is the nightmare scenario for the spooks. You cant gain access to enough points on the network(mobile phones) at one time to track whos sending what. Compared to now where you connect to an ISP who logs where your entering the network.
Isnt the future beautiful, distributed internet,distributed networks,end to end encryption.