I judge Star Gold chances much better (there are to many LH FT on any international LH flight). I can't imagine any situation where there would be as many operational upgrades necessary as there are (after Senators being served) LH FT on board any long-haule-LH flight.

PremEx (as a 'rare' 1Mio Miles UA-StarGold 1K) just got an upgrade to International First on his LH-business-award-ticket (paid with UA miles) on the LAX-FRA segment); he did report this 'gift' in his trip-report.