As far as I'm aware, it's still one session per user login.
In Personas 2.0, using /otcode will open another browser window or tab, but this will result in a separate login with the same user name.
In 3.0, /otcode doesn't work (it gives the message 'Maximum number of sessions reached'), however you can use a separate tab or window and log in with the same user multiple times. This of course will also result in a separate login with a single session.
This is the webgui behavior, so Personas will work the same way. Refer to note 314568 where this webgui limitation is described regarding multiple sessions.