I'm confused. I thought in the French dialing plan, 0 is a significant digit in the first position of a telephone number as in the example given in the other followup about how the French voice telephone numbers by stating pairs of digits.
It was rhetorical. I live in an area that requires 10-digit dialing with a leading prefix for both home and foreign NPA dialing. I don't object the overlay policy that makes use of the home NPA mandatory in the dialing plan, but I do object to the leading prefix. The "1" ain't a domestic trunk-identifying code as no such code was used in this area in the days before electronic switches. It's a legacy of the expanded area code rules, so only very recent, with no explanation as to why it's been retained.