@united_we_rideProgression works on those servers because they are essentially PvP servers. They are open and setup to provide "competitive" play. They are not designed to offer PvE (which would mean all human players that joined would be placed upon the same team).
For instance, when I create my own Portal server I make it so that any humans that join will all be placed upon the same team, so that the end result is humans -vs- bots.
When DICE creates an official Portal server they set it so that joining humans will be placed evenly on both teams, thereby making it a PvP environment. Of course if the servers are empty or have very little humans joining then it has to fill up with bots so then it inadvertently becomes a half arsed PvE'ish place to be... but, since those servers are meant, essentially, for PvP DICE allows normal progression on them.
@united_we_rideTechnically, I don't think those type of servers (empty) should be starting without a minimum amount of joined players. So I don't know why they aren't waiting for more players to join before they start. Either it's a mistake in the way that DICE has set it up OR it's Dice's way of being forgiving to players and giving them an easy way to level up now and then...sort of like a freebie mentality...who knows.
