(Trying TLDR as asked)

Does anyone here happen to live in a country where at least one public GSM network is known to still operate with traditional T1/E1 TRAUs? I would like to try making an international call from my G.711 VoIP system in USA to a GSM MS in whatever country that is served by a traditional TRAU, and see if I can detect TFO in-band signaling within the G.711 PCM sample stream coming from the far end. Or if someone knows for certain some solid technical reason why this idea is doomed, I would appreciate that explanation too.

Reason for my interest: I have a desire to implement GSM 08.62 or 3GPP TS 28.062 TFO, and of course publish the source under a public domain license, but the protocol is complex enough to where I don't see any feasible way to test for correctness other than through actual interoperability testing with an existing implementation.

M~