The Cyrus IMAP daemon can be configured to create mailboxes automagically if the account was authenticated successfully.

You need to look into default-imapd.conf:
# If nonzero, normal users may create their own IMAP accounts by 
# creating the mailbox INBOX.  The user's quota is set to the value if  
# it is positive, otherwise the user has unlimited quota.
autocreatequota: 0
Set to "-1" and mailboxes should be created automagically. In addition the UseSkyrixLoginForImap might be useful for using the OGo password for the IMAP login in the webmailer.