Yes - and no If their Edge is registered to their TB GK, then they need to enable URI dialling on the GK;using CLI: xConfiguration Gatekeeper DNSResolution Mode: (set this to On)through web interface: go to Gatekeeper Configuration --> Gatekeeper, ti...
How about they neighbour their GK to yours - then perhaps add a prefix for calls to systems registered to your GK, i.e. if your system has alias 12345678 they dial #012345678 - which points the call to your GK only, they'll need to strip the prefix t...