Those are actually socket files:
~$ ls -l @/var/run/hald/
ls: cannot access @/var/run/hald/: No such file or directory
~$ ls -l /var/run/hald/
srwxrwxrwx ------------ /var/run/hald/
~$ file /var/run/hald/
As far as I am concerned, '@' before filename is just a pointer that points to a particular port.