As you can see in the Code, the Class has a Property registry.
This is a reference to the global vB_Registry Object (aka $vbulletin).
So as the P?ostbits are being processed within the Class, you can use $this->registry->userinfo['userid'] to get the Userid.
Or in Templates you can (still?) use $bbuserinfo['userid']
If you set $this->post['foobar'], you must also use $this->post in the Template - just $post is smth. different