the drive control unit is finely tuned to the torque input of both propulsion units - engine and motor generators in gearbox. It also very closely watches the ABS module for acceleration sense, incline and yaw.
keeping that in mind - the drive logic is preset with a range of available torque from the engine (CNG even in best tune is only good for 60% of the engines torque). The result is that the MGs will work harder (drain battery quicker, engage engine more to charge up - etc - round robin again)