I personally think it's a good thing - could this act as a deterrent for next time? I think so.
Obviously it wouldn't be right for this to instantly start happening everywhere by everyone. Yes Metro inspectors may not have the powers to do this (and I could see this horribly corrupt justice system seeing the youths as 'victims') however this is definitely better than waiting for the bobbies to turn up with the youths ran away; thus requiring more police resources to find them.
RE: Tyne and Wear Metro