The Servo library uses a hardware timer of the avr chip, but the hardware timer only issues an interrupt and does not change any output pins.
Inside the interrupt, the function "handle_interrupts" is called. This function sets the outputs pins high or low for one or more pins.http://www.arduino.cc/en/Reference/Servo
The tone() function and the SoftPWM use the same technique.
I'm not familiar with DC brushless servo motors.
Can you post a link where I can read about it ?
I have only used normal servo motors (0-180 degrees) and H-bridge drivers for DC motors.
Can those motors operate with a PWM signal ? If you use the function analogWrite, you use hardware timers with PWM output.