Yes and no. It's not MeshCAM creating the faceted surface. Meshcam can only read faceted sufaces, which is what an .stl file consists of.
What you can do is change your .stl export options in Alibre to export a surface with much smaller triangles. This will give you a smoother surface, but never perfectly smooth. You'll need much more expensive CAM software to do that. Also, the downside to exporting a higher res mesh from Alibre is that it will use much more memory, and take much longer in MeshCAM. Increase size slowly to see the effects.