Hi Davide, you can search for the email template which you are using for sending event registration confirmation email under settings->email->templates and then for that template there will be a tab called Email Configuration there you can define your static email CC.

Method 2 : you can also define it at you python code like,

Sample code syntax :

mail_vals = {

                     'email_from':'specify email from',

                     'email_to': 'specify email to',

                     'email_cc':'specify email cc',

                     'subject':'specify subject',

                     'body_html':'specify body',

                     }

self.pool.get('mail.mail').create(cr,uid,mail_vals)

Method 3:  Once you search and get the template id then you can write the required email_cc for that related template to achive the functionality.

Sample code syntax:

self.pool.get('mail.template').write(cr,uid,template_id,{'email_to':'add email to','email_from':'add email from','email_cc':'add email cc'})