The Quadrantal rule is or UK UNCONTROLLED AIRSPACE ONLY.....look at any UK LO enroute chart in your JEPP manual...you
will find 2 levels 'schematics'.
One for UK
uncontrolled airspace, and one for everywhere else.
The 'everywhere else' schematic outlines the ICAO semi circular cruising levels
- for tracks 000 - 179M ODD levels, 180 - 359M EVEN levels. This rule holds up
to FL290....
If you now refer to a HI enroute chart you will find a
different levels schematic.
This will
offer the same rule up to FL290, and then a different rule at and above 290.
This is
because the min separation above FL290 between opposing traffic increases to
2000ft (versus 1000ft below FL290).