This is so obscure I hadn't even heard of it before. According to Wikipedia, it was in effect for 12 days and merely the name given to a union committee running a general strike in the city. It wasn't actually a soviet or council in the real sense of the term - an assembly of workers that acts as a government. They used the term because it had become a popular term thanks to the Russian Revolution. When the strike ended so did the "soviet". There was no actual attempt to keep and hold power.
There is no possible way this group could have taken over Ireland (and there is no evidence they wanted to - again, it was just a general strike in the city). The people with guns in Ireland is limited to the British Army and the Irish Republican Army, which for all of their socialist ideas was not Communist. Whoever is in charge once the Irish War of Independence is over, it'll be one of them.