No decent ISP would block DNS packets between end users and to/from the root servers. However, they are not recursive, so you cannot use them as general-purpose recursive nameservers. They simply serve the root zones and associative glue records.
If they work as recursive servers for your friend on Tiscali, then Tiscali probably intercept the packets a redirect them to their own (recursive) servers, much like many ISP's do for outgoing SMTP connections. This is the 'right thing' for end users who don't know what they're doing, but tends to drive experienced users mad.
If you want a non-ISP recursive server you can run your own (many free ones for most OS's, i use BIND9) or use an external service such as OpenDNS (free).