The Online Multiplayer beta has been dated by EA as the 29th of this month (September).
The beta has also been confirmed to appear on PC via EA Origin on it’s demo page, on PS3 automatically appearing on the PS Store and finally on Xbox 360 again appearing on the Marketplace automatically on the 29th.
If you download the beta on console then you will be able to download and play from the get go, but if you download the PC version then you need to grab the Origin client to be able to play.
The Beta, will consist of the game mode Rush and the Operation Metro map. It will end on the 10th of October.