In the mission editoer there are two choices. Either artillery calls by dedicated spotter-units or free for all. Which is used in real military operations? Art observers (both infantry and vehicles) are rare, and they would probably be used up pretty fast in an allout conflict and I guess other units often are the ones who call for support. Would a tank or infantry unit have the radios to call for artillery? How does it work in SB if you chose the "art calls for all"-setting? Does it set a higher priority for dedicated observer units?