3GPP 23.501 v20.2.0 — the document's own text

5.35A.3.3 UE mobility when moving together with a MBSR cell

Taught in 26. Relays, satellites, femtos and shared networks (The 5G system architecture, in depth).

For a UE served by a MBSR cell, it may observe change of TAC and/or cell IDs, even if it is still connected to the same MBSR. This can trigger mobility registrations, as defined in TS 23.502 [3], if the new TAC is not in the TAI list in the RA.