not completely sure that it will work for 2 way communication... how do you plan on setting up the 2 way radio at the NID to transmit? if you can overcome that hurdle, it still would not be full duplex, unless you used 2 radios on different channels, one for TX and one for RX...
i am sure that this would violate at least 2 laws - theft of a telecommunications service, as well as something for using the 2 way radio in this method, since the best way to do something like this would be on a licensed radio band... and then there is the purpose which you plan on using this, which may result with a 3rd charge of harassment, fraud, or something else... oh.. i forgot to mention, felony wiretap, since basically you would be able to remotely monitor any telephone conversations on the line...
i would recommend against doing something like this... would be a nice project to build for a proof of concept on a phone line that you are authorized to do so with (your own line, or a friend who allows you to test it on their line)
but i think that i am not speaking in the true tone of this board... what i meant to say was... sure do it, and then shoot up heroine and then your school...
=)