i can download, but there are issues. When I subscribe to a faction, it says subscribed and I go back to the game. The leader portrait dont show up, and it might lead you to believe that nothing is happening. In MyGames\Galciv3\Factions, the data is indeed there. I need to then restart the game, and the factions appear normally. But when repeating the test, the factions were in fact downloaded, just no leader portraits initially.
as well, when you unsubscribe or delete the faction in game, the files actually REMAIN untouched in MyGames\Galciv3\Factions. I would think that to be a problems as well, unless subscribing to factions always overwrites what is in there, and Stardock doesn't mind for old trash to collect on our PCs.