Of course (hence my first sentence that you didn't quote), however the practical and sensible things would be to come of at a junction and find a lay-by, public toilets or suchlike. Why/how(!) would anyone stop a coach coming off at a junction? They would not have police blocking every single...
Obviously, doesnt reflect well on the services/police from that article (not that I am sure we're really getting the whole story!)
So, there was not a single junction on route where the coach could have pulled off at and found a lay-by on an A/B road to let the fans relieve themselves? hmmm.