I have a working breadboard version with an atmega328p.  I am testing this device against a cisco vg224 voice gateway with default settings on the line port.  The cisco gateway only puts out 38VDC rather that your typical POTS line from the phone company at 48VDC but I think I should work with that as it would be typical of an office environment.  I plan on porting my code to an attiny84 for a smaller footprint.  Once I make a working board layout and test the ported code I will submit it for sharing.