Servos have their own electronics built-in, and typically use a potentiometer and DC motor inside as you mentioned. However, standard servos do not give the user access to the potentiometer feedback or direct access to the motor leads. Instead, they accept a hobby RC signal and manage the control system internally. You can find more information about servos in our "Engage Your Brain" blog series, starting with this "Introduction to servos" post. Depending on your servo, it might be possible to open up a servo, remove the control electronics, and essentially replace them with the jrk; however, please note that this is an advanced modification that could potentially damage your servo.
I am not very familiar with the SimTools software, but the Maestro does accept TTL serial commands like the jrk. You might try posting on the XSimulator forums to see if anyone there has experience using the two together.
By the way, I was not suggesting to use the Torxis servo for your application (although it might work); I was just using it as an example of how the jrk can be used to create a servo.