The library is specifically designed to decode the 8 DTMF tones. Decoding CTCSS tones is much more difficult because in some cases they are less than 3Hz apart whereas the DTMF tones are at least 70Hz apart.
If you were aiming to decode only a few of the tones and could choose a few that were much further apart, it can be done, but trying to decode all of them is probably impossible on an Arduino without external hardware.
Pete