Answering your questions Roberto below in bold green:
1) How does one obtain a copy of the Habitability Licence for an older property, Maria? For example, an apartment built in 1970? Since this is apparently required now in order to register a property for tourist lets, it would be good to know how to get this. Every Council has its own rules so best procedure ahead is to ask at the Planning department. Better with the help of a lawyer/solicitor. As you well say, in Andalucia, for the obtention of the Tourist license, you need to have the Habitability license.
2) "...it is the document which really comfirms the house is legal ( it has been built or reformed according to the project the Local Council approved)" - in light of all the illegal building scandals, and all the local mayors involved in illegal activities, does this so-called "licence" really have any value today? Yes, they do, unless their validity is being challenged legally or judicially.