How does Lawful Interception works in LTE Evolved Packet System?
3GPP Evolved Packet System (EPS) provides IP based services. Hence, EPS is responsible only for IP layer interception of Content of Communication (CC) data. In addition to CC data, the Lawful Interception (LI) solution for EPS offers generation of Intercept Related Information (IRI) records from respective control plane (signalling) messages as well.
See Lawful Interception Architecture for LTE Evolved Packet System for more details.