On the simple side, yes, many could irish quite fluently, both in the rank and file and the leadership.

The reason for it however is interesting. Due to the huge numbers of men arrested in the early seventies there were hundreds of IRA members held in temporary prisons and they took the opportunity to create a more educated soldier, people who had been wrongly arrested where convinced to join up, those who had joined in anger of the violence were taught political theory and history, and those that were knew what they were about debated about issues and tried to define what the ultimate goal for the IRA was.

Eventually however their freedoms were further restricted, prisoners were moved into permanent prisons and held in cells in pairs or singles instead of the large communal huts of before, because of this communication became shouting from cell to cell, out windows and under doors making what ever they were talking about extremely obvious, it became impossible to plan escapes, discuss orders or protests or even have personal chats. In this environment the teaching of Irish which had started in the internment camps became increasingly important as it allowed IRA members to talk without the 'screws' being able to understand what they were saying.

Irish was taught so throughly in prisons that they were dubbed Jailtachts, a play on the Irish term Gaeltacht meaning an Irish speaking area. Many IRA members left prison bilingual and adopted the Irish translations for their names.