And a slave cannot "login" to that bus, it just listens on the bus for commands from the master and replies if it's instructed to do so.
So it's just need to be set as a slave for instructions purposes only! 
Do you know a what baudrate theat EasyVR Commander is communicating with the module?
When at SW bridge mode, the same as the serial monitor:
if (bridge.check())
{
cli();
bridge.loop(0, 1, 12, 13);
}
// run normally
Serial.begin(9600);
//while(!Serial); //for when I need to debug the setup via serial monitor.
port.begin(9600);
if (!easyvr.detect())
{
Serial.println("EasyVR not detected!");
for (;;);
}
easyvr.setPinOutput(EasyVR::IO1, LOW);
Serial.println("EasyVR detected!");
But from the manual:
The initial configuration at power on is 9600 baud, 8 bit data, No parity, 1 bit stop. The baud rate can be changed later to operate in the range 9600 - 115200 baud.
When in PC mode, from the manual, again:
The full speed used is 230400 bit/s, but the option “Slow transfer” can be used to reduce it to 115200, for better compatibility with slower serial adapters2. One adapter that can go to full speed is the SmartVR DevBoard. Otherwise any USB/Serial adapter with TTL/CMOS interface can be used for updating the flash. The EasyVR Shield can be used for the download, provided that the jumper (J12) is in UP position.
To help you further with this stuff, I need the schematics of the EasyVR shield.
I asked the support guy via email for this, let's see what he replies!
Thanks!