(Pat, please mask my email address. Thank you.)
France went to all numbers in the late 60s, or perhaps in the early
70s, a result of the rebuilding of what had been a very creaky old system. To force people to use numbers instead of letters, all phones from then on only had numbers, no letters and this for some 20 years. Phones now have letters and numbers, as before.As was pointed out, they went to 8n with two digits 0x, to identify the area called. Finally, the first two digits became mandatory and represent the 4 areas, Paris area (01), then the north, south east and south west. The first digit became a way of permitting competitors to offer service directly to subscribers. Thus, if one were using tele2 to make calls, one would dial 4x-yyyy-yyyy instead of 0x-yyyy-yyyy.
-er