So the summary is:
BA list is obtained from SI5.
SI5 is obtained from BCCH of
serving cell.
Measurements are done on frequencies present in the BA in list.
Measurement reports are send to BSC.
BSC after analysing measurement reports shortlists a BETTER carrier.
After that if this BETTER carrier is ALSO present in NEIGHBOUR LIST then handover command is given to MS.
After that MS performs an handover attempt.
Result may be:
Handover successful
or
Handover Failure(for reasons as discussed earlier).
Kindly confirm the above!