Anyone know which places use PANS-OPS to define procedures and which use
TERPS, and why? Is there a historical or political context to this? Why
do international authorities go to such lengths to maintain two systems
which essentially accomplish the same thing?

I just got a bunch of stuff from France, listing the changes to be
implemented over the coming months in their approach plates, as a result
of the latest developments in PANS-OPS. Looks pretty good too - they're
putting grey shaded blocks in the profile view on non-precision
approaches to indicate minimum safe altitude for each segment - a very
readable solution for "dive and drive" operators.

GF