OK answer the question of what they are celebrating in the clip I have posted. A simple answer.
I was over in Dublin not long before the vote and the streets were filled with yes and no material to the abortion, barely a street light without a yes or no board on it. It was a huge deal on the ongoing battle between old Catholic Ireland and a liberal secular Ireland. It was a very heated debate, and was always going to have a sense of relief and celebration for either side of the debate that ultimately came out on top in the referendum.
In addition, in 1992, Ireland effectively legalised abortion as long as you were willing to travel outside of Ireland for it. Constitutionally, a blind eye was being turned to it being done elsewhere, and for that reason, 1,000s of Irish women a year were travelling to the UK or elsewhere for an abortion.
So, celebration wise, it goes a lot more far-ranging than this basic idea you have that these people are all celebrating the actual act of abortion (which was already legal if you had the means to get elsewhere), but actually for the win over what many view to be the stranglehold that Catholicism (a male-dominated religion, like most) has had over the direction of the country, as well as women to have that right to choose to have the procedure undertaken close to home.