Solution found: was a misconfiguration of Libvirt: if I pass the usb TA isdn(usb redirect) the TA is recognized by the vm, but as I said the outgoing calls fail, the incoming calls make the “phone” ring, but at answer fail.
If I pass a pci-e usb adpter(need vfio/iommu) then I connect the usb Ta to the adapter works all fine.
The configuration files are little different and posted in this post