I wouldn't say we've never seen it, Octy. We certainly had gangs up above in Dublin in my youth and they weren't gangs of little angels but they were area based whereas this mob seem to be based around the culture of Gangsta (C)rap music so they probably have far greater potential to grow in number. You still see gangs of youths hanging around the northside suburbs, again not gangs of little angels... but probably as likely to shoot you as stab you these days.
What we've never done is dealt with it. The Gardai invariably bring the Public Order Unit into an area after a disturbance or shooting or stabbing but they know they're fighting a losing battle.... shutting the stable door after the horse has bolted.
How would you like to be driving one of the buses the Ashbourne gang fled on, safe in the knowledge that the Gardai are happy that they're now your problem? One driver -vs- 40 armed boys and girls and the Gardai conclude there was nothing to see there... more luck than judgment in the outcome!