I successfully used my own router. You need to clone the previous MTS router MAC address, as well strip vlan off of the connection to the fion modem.
In my particular case, I have a buffalo (N600) router flashed with dd-wrt. It does not support vlan, only tagging. So I presume it ignores/strips vlans off of incoming connections (Im guessing, I dont know a great about of vlans). And like I said above, I also cloned the MAC address. With dhcp for the WAN port, it pulls an ip and works great!