well, when the ms is in dedicated mode, it gets all the SI msg on the SACCH. At call release, it already knows what are the neighbours in dedicated mode (si5) and in idle mode (si2), and the fact that the cell is barred : all this was sent during the call, on the sacch.
Regarding the 3GPP… good luck 🙂
Look in series 4x
– for doc titles with “idle mode”
(there are 2 of them, one about “non access stratum”)
– for doc titles with “multiplexing”
– “link control”