So far, I have not found any relevant information about the Palermo Court Prison. Concluding from the stationery below, this prison also served as a transit point before being transferred to Ustica concentration camp...
Stationery, written in Palermo Court Prison (15.III.42), censored by prison censor (17.MAR.42) and sent through Palermo Ferrovia (18.III.42) to Split. From the message: "... I am in the transit for the Ustica concentration camp ...".