Well...
As of last week, it was just Hornady for the head stamp.
However, Hornady just announced the return of Frontier ammunition, loaded in the Lake City plant, with LC brass.
So:
Hornady and LC, soon.
I don't know about any Frontier/Winchester cross-over. The reason Frontier Cartridge was formed by Hornady was specifically for ammunition and brass production (initially using LC brass, just like the reincarnation - later producing their own, before transitioning to the Hornady head stamp).