Pls explain what you mean by that?
Eg call with mobile to your ATA and than from there call via VoIP.
We do something like that in AU, some phone companies allow you to nominate a number you call for "free". This can be your home number than use the ATA or pbx to divert to another number.
The trick with the PBX is that only a pre configured numbers can be used. I believe we can make the ATA work to collect DTMF and than dial accordingly.