So was digging around the XcomLW_Activities.ini and found these:
MIN_REBELS_TO_TRIGGER_INTEL_RAID=6 ; Number of rebels on intel job to make this mission trigger
MIN_REBELS_TO_TRIGGER_SUPPLY_RAID=6 ; Number of rebels on supply job to make this mission trigger
MIN_REBELS_TO_TRIGGER_RECRUIT_RAID=6 ; Number of rebels on recruit job to make this mission trigger
Thought some people might find it useful for Haven management (I didn't realise this missions existed so I assume others might not know ether).