This is a task that requires expert knowledge from areas of radio telecommunication and digital trunking protocols. Rather rare set of skills. I have them as I have previous experience in the field of cellular communication (UMTS/HSDPA), trunking systems (both P25 and Tetra), high-speed wireless links (OFDM). I'm experienced C, C++ and Python programmer, personally prefer targeting Unix systems, than Windows - but in this case I can prepare highly functional and usable tool for Windows.
DISCLAIMER! The task can be finished only of delivered WAV files have enough quality to carry 4PSK signal without BER above minimums required to correctly decode symbols.
Please provide more information about expected format of output files. If pure strings containing hexadecimal numbers in single line per message is enough - please state it clearly. Please declare if you require any timestamps for every frame decoded or not.