Oracle provide an excellent utility, SQLTXPLAIN, that provides enhanced query plans, details on table statistics, column histograms, the Oracle parameter settings in force in addition to the 10053 trace.
This HTML report can be an invaluable aid to analysis of how a complicated Siebel query was parsed.
SQLTXPLAIN is described in more detail on Metalink (Note 215187.1).
Here is an example report produced by SQLTXPLAIN for a Siebel query related to the 'All Accounts View'.