EKF2 fusion of vision position estimates in Altitude hold flight mode

ArduCopter Copter 4.0
1

Hello Everyone, Please I have a question regarding how EKF2 fuses vision height measurements in Altitude hold mode.
Here is my question:

When we set EKF2 to use Barometer, and we still transmit vision position estimates (including height measurements), does EKF2 fuses the vision height estimates? If so, in altitude hold mode, will the vision height estimates be used?

Cheers!