in the standardjbossjdbc-cmp.xml file I found an entry (I forgot the tag name) in the mySQL section where it said "FOR UPDATE". I guess that applies for the SELECT...FOR UPDATE queries. But when does the CMP 2.x engine use these instead of simple selects?
Set row-locking to true and you get SELECT...FOR UPDATE on the databases that support it. On other databases you get different syntax.