and for the time that user001 execute the imap 'list' command, this is the log trace in dovecot:

Sep  9 13:09:12 imap1 dovecot: imap(user001): Debug: Namespace : type=shared, prefix=shared.%u., sep=., inbox=no, hidden=no, list=children, subscriptions=no location=maildir:%h/mailSubDir:INDEX=~/mailSubDir/shared/%u Sep  9 13:09:12 imap1 dovecot: imap(user001): Debug: shared: root=/var/run/dovecot/, index=, control=, inbox=, alt= [...]

Sep  9 13:10:44 imap1 dovecot: auth: Debug: master in: USER   1       user002 service=lib-storage Sep  9 13:10:44 imap1 dovecot: auth: Debug: ldap(user002): user search: base=dc=example,dc=com scope=subtree filter=(&(objectClass=CourierMailAccount)(uid=user002)) fields=mailbox,homeFilter Sep  9 13:10:44 imap1 dovecot: auth: Debug: ldap(user002): result: mailbox(mail=maildir:/var/maildir/%$)=vol05/4/40/user002 homeFilter(home)=/var/mailfilter/vol05/4/40/user002 Sep  9 13:10:44 imap1 dovecot: auth: Debug: master out: USER  1       user002 mail=maildir:/var/maildir/vol05/4/40/user002    home=/var/mailfilter/vol05/4/40/user002 Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: auth input: user002 mail=maildir:/var/maildir/vol05/4/40/user002 home=/var/mailfilter/vol05/4/40/user002 Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: maildir++: root=/var/mailfilter/vol05/4/40/user002/mailSubDir, index=/var/mailfilter/vol04/4/46/user001/mailSubDir/shared/user002, control=, inbox=/var/mailfilter/vol05/4/40/user002/mailSubDir, alt= Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: acl: initializing backend with data: vfile Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: acl: acl username = user001 Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: acl: owner = 0 Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: acl vfile: Global ACL directory: (none) Sep  9 13:10:44 imap1 dovecot: imap(user001): Debug: acl: Mailbox not in dovecot-acl-list: shared.user002.INBOX