Order and Destruction only find common cause in the most desperate of circumstances. Units from the Forces of Order always treat units from the Forces of Destruction as being desperate allies, and vice versa.
Units in your army treat desperate allies as enemy units that cannot be charged, shot or targeted with spells. The only time that desperate allies count as friendly is if a spell or other effect causes damage to friendly units.
In this case the desperate allies will be damaged as well, just like friendly units would. This means that, for example, desperate allies units:
Cannot use an allied General's Inspiring Presence special rule.
Cannot use an allied battle standard's Hold Your Ground! special rule.
Cannot be joined by allied characters.
Have to take Dangerous Terrain tests when fleeing through allies.
Are not counted as 'friendly' units from the point of view of targeting spells.
Do not cause Panic tests in allies.