I mean, for the purposes of `libphonenumber`, PrioA-D is not used. Also, as far as I know most things are sent out-of-band anyways, but I wouldn't be surprised

I mean, for the purposes of `libphonenumber`, PrioA-D is not used. Also, as far as I know most things are sent out-of-band anyways, but I wouldn't be surprised if there's some legacy system out there which work only on DTMF.