epon

im trying to get my sophos xg210 up and working on xfinty it works on another cable provider  on coax  the xfinty is on epon  with XER10   but the threads say this Third-Party Routers: In eligible communities, customers can now connect their own third-party retail Ethernet routers directly to the ONU at no additional cost. but t1 when you call in will not help at all  i moved from another provider that my equment works fine but now i'm told its incompatible ? by t1 and will not escalate at all