There are two ways that brushless controllers work. The most popular and inexpensive solution is to use sensorless, the controller monitors back emf in the windings and asseses the postion of the motor and switches the feed to windings accordingly.
The second type uses hall effect sensors which are positoned at 120 degree intervals (to represent the thee phases) around the motor, and sense the magnetic fields feedign back to the controller.
These give much better low speed control, as good as a brushed motor, but the controllers are expensive, and limited in voltage range.
For scale applications a good brushed set-up is difficult to beat. Very high quality motors like Buhler, Pittman, Maxon that will out last the owner in model applications and are available for peanuts if purchased surplus, and a suitable controller is inexpensive too.
They offer superb low speed running with multipole armatures, and are very efficient.