Yes, we have used it before with robotC
You will need to use 3rd party robotics suite:
http://botbench.com/blog/robotc-driver-suite/
(it is included with RobotC 4 - so if you use RobotC 4, you do not need to download anything, just set the correct path for include directories)
The suite contains sample programs for using sensors with the multiplexer which will help you write your own code. If you want, I can share our code.