MecaStack does not consider ice on guy wires. There are two issues the weight and wind area. You could take the additional ice weight into account by artificially increasing the weight; however, this weight increase will be present all of the time and so you may want to consider creating a separate MecaStack run if you take this approach. As far as wind on guy wires, that is not considered by MecaStack. The application of wind to a catenary cable member is very complicated, and beyond the capability of the software. Typically the wind load on the cable is small in relation to the wind on the stack itself.
Typically codes require ice be considered with a wind load that is much less than the design wind load. Therefore the "Ice" load case is typically considered with a wind load that is very small compared to the design, and rarely controls the design.