You don't get any COS bonus when flying economy (doesn't matter if it's full Y or discount Y)! The whole idea of COS bonus is to reward you for paying premium fares which economy is not. Now, if they started selling seats in the cargo area then economy could be viewed as premium... Until then, no COS bonus for economy.
With UA and LH you still get bonuses for being a frequent flyer (Premier, Senator...) when you fly economy.
[This message has been edited by NYC1 (edited 12-12-2001).]