Thanks everyone.
Here is the info I could find on the airside shuttle so far. Does this seem accurate, and does anyone know if I can get the bus back from terminal B to C?
From the United map you can see that the airside bus departs from terminal A2 and ends up on the right hand side of Terminal C. From digging into the official map the bus seems to depart from near gate A28 in terminal A2, and arrives near gate C73 in terminal C