Someone has been posting the listening comprehension exams from previous tests on YouTube and posting the questions on their blog. I have not managed to find the quaderni for these exams, but I have found the chiavi di soluzione delle prove and have uploaded them to my Google Drive. Note that the answers are provided for all the exam levels in the PDF, not just the C1 and C2.
Regarding specifically the C1 and C2 exams, one thing that I have learned from doing so many of the practice exams is that prova n 3 is the most difficult for me but there are always 6 answers that need to be selected from the available options in this exam and it seems to have been this way for at least a decade. So, if you are finding this exam to be a little difficult, knowing that there are only six correct options may help you narrow down the correct ones. I'm not quite certain if this type of test exists in the B levels.
Here are the exams that the person mentioned above has uploaded thus far for the C levels.
Livello: C1 Modelli di esame di Italiano - CILS Dicembre 2013 - Ascolto
Livello: C1 Modelli di esame di Italiano - CILS Giugno 2014 - Ascolto
Livello: C2 Modelli di esame di Italiano - CILS Giugno 2013 - Ascolto
Livello: C2 Modelli di esame di Italiano - CILS Giugno 2014 - Ascolto