(this is assuming Herr Burt has not made all the empires and neutrals allied to all cartels)
This currently holds for The Forge and other traditional alliances servers.
It's good to point this out to people. Thanks, Bonk!
BAck when I first started working on Econ War, I spent a long time playing with the tensions levels and the gf settings. I can't make it so you always get a mandatory mission in enemy cartel space and never get one in allied cartel space. As Bonk says, the empire layer simply plays too large a role in determing where mandatories appear.
However, after playing sufficiently with the gf and tensions, I got it so that you should get more mandatory missions in enemy cartel space (reasonably often) than you do in your own cartel space (fairly rare).
I figured this actually makes sense in a pirate campaign. It's OK not to get a mandatory in every enemy hex, since pirate cartels don't maintain deep layers of listening posts and large fleets of dedicated picket boats. It's OK to get occaisional mandatories in your own space, since even at home the police are out to get you.
-Herr Burt