I THINK we have figured it out. Based on testing:
- the Prussians need to control not only the three regions around Pirna, but have Pirna itself under siege; control means MC of 60 or more; the Prussian control condition is satisfied by MC above that level, they need not keep units in the region (although its obviously risky to leave them unattended)
- when and while the Prussians have those conditions fulfilled, there is a 75 percent chance per turn the Saxon Capitulation will be triggered, up until the end of 1756 (when it lapses if not yet triggered)
- while the Saxons can deploy outside Pirna to fight and activate, it is risky and the only reason for doing so would be to try and free up one of the regions the Prussians need to occupy for the trigger event; if the event triggers the Saxon Army, wherever it is, disappears
- if the Saxons stay inside or are driven into Pirna, unless the Austrians free up one of the regions, the Saxons only hope is if the Prussians get bad rolls on the capitulation trigger checks until the event period lapses at the end of 1756
- we ASSUME that if the Saxon capitulation event, for whatever reason, isn't triggered, the Saxons are treated per normal as an Austrian ally and Pirna needs to be taken by siege or assault per usual
We also agreed to the house rule that the Prussians should not hammer the fixed Saxons with a mass assault on the camp on turn 1 if they were inside Pirna; they were fair game if they deployed outside of course or tried to escape; otherwise Prussia would try to trigger the capitulation event. The house rule lapses at the end of 1756.
Does that sound like we have it figured out?