This specific memorandum concerns the chance of asking for the turning of not allowing to work visas into self employment residence papers (as provided for by Regolamento di Attuazione art. 39 paragraph 7). This chance could be used only by people having entered Italy before the enactment of flows decree on march 15 2002. It seems that when a person has entered Italy after this date, he/she cannot access the turning. This “cannot” is written in the quoted memorandum but it is not confirmed by Regolamento di Attuazione art. 39, which simply says that someone regularly living in Italy on different to work basis can ask for the conversion here in Italy to self meployment residence papers, in case the visa is still valid and self eployment quota are available.
Remember that you need to ask local labour department to certify the availability of quota.
We know that there are still available quota because offices are still releasing certifications. These quota were enacted by decree (the 2002 flows decree extended to March 31 2003).
To answer to Trento question, unfortunately the administration is right, in fact turning a seasonal work permit into a self employment one is not possible. In fact the turning is possible only if a person holds a permit not allowing to work.