>ISTR +1-888-xxxx being the international equivalent of 1-800-xxxx
Close, but no. The prefixes for international "caller pays" calls to
US toll free numbers are:
(800) xxx-xxxx -> +1 880 xxx xxxx
(888) xxx-xxxx -> +1 881 xxx xxxx
(877) xxx-xxxx -> +1 882 xxx xxxx
(top of the page)
I know that's not an "official" source of information, but this page
does claim that they intend to deallocate those area codes soon.
I suspect it is because, as the number of toll free area codes increases
(866, 855, 844, etc..!), it's becoming a burden to have to allocate a
"mirror" code in each case as well.
Anyway, I believe it's possible to have a toll free number that's only
dialable in one area and have the same number allocated to someone else
who has a toll free number only dialable from some other area, as long
as the areas don't overlap. So who would the international caller reach
in that case?