If you fly an "RA" TCAS event, then the autopilot and Auto throttle should be disengaged. TCAS "TA" is to alert crew of other "traffic" but is not deemed to be a threat.TCAS "RA" maneuvers are generally flown with "smooth" control inputs for pitch up or down depending on the course of action. These events are not subject to high or low pitch angles in general, so MCAS probably wouldn't be a factor.
I'm not a pilot, but what about
: "Terrain! Terrain! Pull up!" ?
From what I have heard in that situation you may need to pull up until the stick shaker activates, and then keep around that AoA until you clear the terrain, with the stick shaker activating intermittently, as demonstrated in this simulator session (the relevant part of the video starts at 13:30):
Could MCAS interfere with the terrain escape maneuver? I think that could be the worst moment for MCAS to activate.