The "ER" reserve is 24 hrs. There is no 12 hr SC window only 24 hrs. First 12 you can be used for a domestic or international rotation, next 12 is for a international only. Still six a month with can cover 12 total days of reserve. It stinks but it is contractual.

Basically if it is legal under Whilow you can do it, and then be legal for any and all flag ops.

SLC crews would probably do the CDG trip that is now crewed by other bases, and maybe a few HI turns if they go back to the ER.