In if fully put into play there are three levels of control and it's been a while since I read upon it butvill trybto capture it as best I can: director or automatic control is where the guns of a given type are slaved to a director with a gun plot with mechanical computers as intermediaries which allows the director to sight in all guns on a single target and this version often used radar and range finders in the director. The gun computers issue orders to match each of the turrets with the target the director is targeting. Depending on the number of directors and computers the main or secondary battery of a bb could be split between targets. There are limitations .... the computers dealt with combinations of weight and powder unique to their own systems so you would not control a 5 inch gun with say a 16 inch computer but you could use a 5 inch director and tie it into a 16 inch computer because the director only supplied projectile independent variables.
The next is pointer control where the sighting data from the computer was sent to displays in the appropriate sections of the turrets and the trainers and pointers matched the data sent to them. It's basically director control with a extra step and this was considered a back up most of the time.
Third is local control where each turret is more or less firing at their own targets using backup computers inside the turrets themselves and getting target data from range keepers in the turrets themselves.. the ears on many turrets house the mirrors for these range finders.
Depending on the era some or all of these features would be present. On an iowa you could get target data from 9 directors the two mk 38 directors, the 4 mk 37 directors, the mk40 director in the armored conning tower, and at a minimum also turret two which tended to hold onto its stereoscopic range finder while the coincidence range finder in turret 1 and 3 were removed (depending upon the time in question) there were two main battery plots with computers and I think at least two secondary plot rooms with two mk1a computers each so right there you can fight two targets with the main battery and 4 with the secondaries. All thr mounts could do local control but accuracy would suffer.