[thejeff]

As far as movement goes:
In each phase (ritual or normal) all movement is resolved before any battles are. In the ritual phase, all teleports, remote summons, etc take place, then any necessary battles are resolved. I believe those occur in UnitId (or reversed UnitId) order. That also applies to remote attacks, such as Mind Hunts. They may or may not find teleporting mages depending on that order.

Magic phase battles do not prevent armies from moving. Except, of course, armies that lose.

In the normal phase, all movement to friendly provinces happens, then into enemy provinces. Order is not important. In three province example where A->B->C->A, (all different nations) each movement will succeed and a battle occur in all 3 provinces. No army would be caught or pinned down.
Only when an army is invading a province from which an enemy army is attacking them is there a chance of the army not moving. In that case, A->B->A, both armies may fight in A or in B or may miss each other and swap provinces.


There is (or was?) also a rare, but sometimes repeating, movement bug, where armies will refuse to move.