Star Alliance cross ffp upgrades are only on Y & B fares
http://www.flyertalk.com/forum/star-...-y-b-only.html
http://www.staralliance.com/en/benefits/how-to-upgrade/
http://www.flyertalk.com/forum/unite...-carriers.html (United but typical)

People in the TK ffp may be able to upgrade an L fare with TK ff miles