The diagnostic mode just lists the cells and their parameters afaik. It doesn't capture IMSIs or traffic to/from other devices like this does. It's like the network diagnostics menu built into Samsung and Apple phones.
It isn't even able to list some crucial parameters needed to identify neighboring cells. It's simply dumping data that's already used by the modem for its regular operation.
It does, however, more than just "listing cells" though. You can sniff all the comms, but only between your device and the base station. It won't listen to anything else, you need SDRs for that.
