Apparently it is still out there, the RBO in 10g and even Oracle 10.2.0.2.0, as demonstrated by Eric, and i thought that it was already had gone. Especially in Oracle 10gR2. Maybe not internally, but untouchable by us mere mortals.
I saw the following post of Eric Jenkinson in an OTN forum( http://forums.oracle.com/forums/message.jspa?messageID=1499581)