jxn_30 Disabled dispatch centers:
If a dispatch center is disabled, the buildings assigned to it can no longer generate operations; the above-mentioned cases for minimum requirements are independent of this.
I have 8 DC's deactivated and only one activated as a main spawning DC.
I spawn 645 Fire missions as that is how many fire stations I have, disabling the DC's will still generate your total mission count.
You're slightly confused..
You generate (your highest number of stations + 1) missions, but that does not mean each of those stations generate a mission. This wouldn't work as a set up with 200 fire, 100 police, 100 ambulance, can only generate 201 missions, yet will generate a mixture of police/fire/ambulance calls (providing none are disabled).
Only stations in active dispatch centres can generate a mission, however, one station can generate an infinite number of missions. This can be seen by the location that missions spawn, and by viewing a spawned missions info for "generated by", followed by a station.
Theoretically, you can have it so only 1 fire station is enabled, and still spawn 1000 missions. They'd all just spawn within radius of that station, and also be limited to what different missions can spawn.