It would probably take a table saw or hand saw... A real tool. I have never actually consider this. The problem may be how the plastic would react to being cut. You cannot cut it with scissors ! If I had a spare I would try it out for you, but I don't . Great idea though.
It is plastic, but you can cut them. I have a heavy duty pair of scissors that were a give away from a department store, they work great?! I have cut mine down to sizes so I am not always rebuilding small lego buildings or lawn items. Hope this helps.