For example, I have a brush-less outrunner with 14 poles and 12 stator windings. It has three connectors. Can this motor be controlled in a way that it performs a single step of 30 degrees (360/12)?
Any stepper motor can be microstepped. If you microstep, you can theoretically go as crazy as you want, but as you increase the number of microsteps, although you increase your resolution, you decrease the accuracy of the step.
In regards to the original question, the smallest angle you can rotate is 8.57 degrees with a 14 pole 12 stator configuration. You can find a detailed explanation of this system here: http://www.aerodesign.de/peter/2001/LRK350/index_eng.html by clicking on the link for "Why does the Torquemax rotate so slowly and so forcefully" and scrolling down.