As a former PS2 player of a few years, the correct answer is "not well."
When you get into the larger battles, several hundred players all fighting, then you get issues of infantry or vehicles not rendering or popping randomly into and out of existence. You get hitreg crap going on. We had a "RecordSmash" battle where the PS2 devs unlocked the player cap on a server so that we could get the Guinness record for the most players in an online battle. That was an absolute mess. In the main battle it was just people spamming grenades/rez grenades.
The main issue with PS2 was "clientside" where each player would have the instance on his machine, including the locations of other players and all weapons fired or movement made would be calculated from your computer and uploaded to the server, and then sent on to other players. So in a fight, from your perspective, you might make it behind cover but on an enemy's screen it still looks like you are in the open. So you get shot and killed even though there's no way a bullet could have hit you. For me this is the biggest issue with mmos like SC and PS2. There needs to be an excellent networking foundation that isn't cludged together (ahem, I love ED, but c'mon, really?? fix your network code!). In PS2s case it was even worse, because they released the game before it was fully optimized. So the mixture of lag, frame drops, warping and so on made a lot of people's first experiences in the game very poor. I think this has mostly doomed it to being a low-pop game when it could have been very good and more popular.
So, anyway, the whole network angle is the part that I am interested in the most. If SC or Dual Universe can get something working that minimizes "clientside" and makes for a mostly bug free mmo fps space experience, I will be amazed.