Hiya Brian,
Gerber's equipment is very good, so I don't see any reason why the plotter can't cut sandblast mask. Just be sure to use the 45° or, ideally 60° blade. No pun intended, but the 30° won't cut it
I've used the older Gerber 15" plotters to cut just about everything. I prefer the reliability of a sprocket fed plotter when it comes to cutting sandblast mask and reflective materials.
Checkers