SIP Early Media (or Cut-Through) with SIP Trunks

I don't have an r in my outbound Dial String - it was the first thing I checked.

I have been researching this, and it's driving me nuts - here is the scenario:

Analog FAX Machine -> Digium TDM410 FXS Port -> Asterisk 1.4 (trixbox 2.6.1) -> Paetec SIP Trunk -> PSTN -> Time Warner TDM Pri -> Asterisk 1.4 (trixbox 2.6.1) -> NVFax Detection -> FAX-2-EMail.

So (in case you haven't played with it) FreePBX does FAX detection on DID's silently - it doesn't generate a FAX answering tone, but instead listens for the "bleep" ... "bleep" ... "bleep" of the sending FAX machine, and if it hears it, then switches to FAX reception mode where it DOES generate the FAX answering tones and begins the reception. This is a Super nice feature of FreePBX because it allows people to give out one number, and yet they can receive FAXES, Voice Calls, and if they have Follow-Me set up, can even answer the call on their Cel Phone - still while only giving out one number!

Problem is, when you send with the scenario above (or if you hairpin and send to another DID on the same SIP trunk) the receiving Asterisk (using the Passive Detection described above) never hears the bleeping of the sending machine (even though I can clearly hear it), and so it never starts a receive and the FAX fails.

All other scenario's work - all Inbound methods work great (on SIP Trunks no less!!!!) and all outbound works fine too as long as the receiving end sends a FAX receive tone - it's just the Silent Answer from FreePBX (NVFax and SpanDSP) that doesn't seem to work.

Paetec took a packet capture today and said they were not seeing RTP from the Asterisk, but this was a bug that was fixed in Asterisk 1.0, and has been (supposedly) working ever since - I have also tried progressinband=always, no, and never to no effect.

I don't know if I trust Paetec's packet capture, so I will probably do one of my own tomorrow, but, has anyone else seen this? If I get this working, then Paetec will be the ultimate SIP Trunking provider, because EVERYTHING WORKS except for this - so close, and yet so far...

Greg