Movement order and fortifications

[Lunaticus]

I found the discussion on movement orders very interesting. Do the experts now the movement and fighting order when a fortification is involved?
1. If an army is besieging a fortification and the army inside breaks the siege there will always be a battle even if the besieging army tries to move away?
2. If an army inside a fortress tries to break the siege and the besieger reinforces will the reinforcement take place before the battle?
3. If an army inside a fortress breaks the siege and another army also attacks the besieging army will both armies be able to join before attacking the besiegers?
My (pretty newbie) estimate is yes to all three questions...