PAT: Please do NOT display my email address where ever it might appear!
On Thursday 5 Jan 2006, Mark Crispin wrote in "Re: Cost of POTS w/o Long Distance":
The old 10-XXX+ Long Distance Dialaround code format is totally obsolete now. It was replaced by the expanded 101-XXXX+ code format over a phased period in the 1990s. Those previously assigned 10-XXX codes were permissively dialable as 101-0XXX, or the "so-called"10-10-XXX or "ten-ten". However, that is a misnomer, since there were also 101-5XXX and 101-6XXX codes in use during the transition, since it turned out that under the shorter, older format, there had never been any 10-10X codes, nor 10-15X or 10-16X codes. Thus, permissive use of 101-0XXX and new 101-5XXX and 101-6XXX codes didn't conflict.
By 1998 in the US, and 2000 in Canada, the expanded 101-0XXX+ format was mandatory for calling the previous 10-XXX+ codes. And since 2001, in addition to 101-0XXX and the "new" 101-5XXX and 101-6XXX codes, there have been codes from the entire "generic" range of 101-XXXX.
However, it might be a long time before the four-digit -xxxx format would run out. I don't know if the plans are to really expand to10-xxxxx, i.e., '1', '0', and then five posssible 'x' digits, i.e., where the third digit in the full dial-around code could be digits other than just '1'.