There are said to be two different types to play the multiplayer. There is the classic Deathmatch and the Counter-Strike type Dark-Ops. Each type has its different scenarios to go with it. (Note for all these scenarios there is Individual Player and Team versions as well).
Deathmatch has 8 different scenarios from what I have found through out the web:
Capture the Flag - This one is basic, who ever hold the flag longest through out the match wins.
Kill Count - GE/PD style. Who ever gets the most kills by the end of the match wins.
King of the Hill - An old scenario from PD. In this one you have to hold a particular spot of a map for a predetermined amount of time to get points. Who ever has more points by the end of the match wins.
Pop a Cap- Another old one from PD. When the round starts one player, be it human or Sim, will be marked as a target. Your mission as the target is to survive for a predetermined amount of time to get a point. When you do survive that time, the timer starts again for you to get another point. As the non-target, you want to find and kill the target to one, stop them from getting points and two, become the target to start racking points in. This scenario tends to get high paced in PD and will certainly in PDZ.
Hold the Briefcase - This is a scenario built off of CTF. There is a briefcase lost in the map. When you find it, get it and a timer will start (with a set amount of time) . When that timer runs out, you will get a point, and the timer starts again to get another point. If you do not have the briefcase, find the person that does and kill them, simple.
Assault - From what I can tell this seems to be like UT Style. You'll be given a mission to do a certain amount of things, like infiltrate the opposing base, open the main gates, shut of the communications circuit and take over the control room sort of thing. This scenario will probably lend itself to more Team based action then individual play.
Territories - Similar to KotH, this will probably be a more advance version. You'll be set up to hold an area and defend it (maybe multiple spots) at the same time. You'll probably have to hold down the areas for the longest time possible and the longest time recorded, that person or team wins. This sounds to be, again, like Assault, more of a Team based scenario then player vs. player.
Hacker Central - In this scenario, you are given the Datathief. You are to find the computer Terminal and using the Datathief, uplink to it. When you do, you'll get a point. The problem is that you will be almost defenseless when uplinking, so be wary of your surroundings.
Dark-Ops - Dar-Ops is a CS base mode. You'll buy weapons before each round and you'll only have one life for that round. who ever is standing at the end of that round wins it (team based versions, the team wins).
Scenarios for Dark-Ops are still sketchy, so i will have to update them later on.
Like in PD, there will be a set of challenges that will most likely unlock most of the multiplayer stuff (maps, sims, scenarios, etc.) and will bring the playability of the game up a notch or two
Sims are suppose to have 3 levels of customizability. Only one is confirmed, which is the Difficulty settings (Mestsim, Easysim, Normalsim, Hardsim, etc.).
The other two I can guess on from these interview statements:
"We're aiming for a similar amount [of customizability for the bots]."
"The bots can now do a lot more than those in the original Perfect Dark, such as use vehicles, roll, melee, and disarm players. You can also have a much greater number of them without the game slowing down." - Lead Single-Player Designer Chris Tilston
The second layer of customizing sims will probably be similar to the special mind sets (vengsim, peacesim, rocketsim from PD) or something close to it.
The third layer of customizing sims will being able to change their models, features, names; just like in PD.
Vehicles are available only in certain maps. Each vehicle can hold a certain amount of people (except Hovercraft, as many as you can cram, is as many as you can get. Go for the world record ) .
Team specific rides can be gotten by the opposing team, but must be "hot-wired" by most likely the Locktopus.
The vehicles are also prone to damage and will be destroyed if shoot full of bullets, but are said to be repairable.
-Environments are fully destroyable.
source found HERE