Complex sentence: The IRFU also insisted on International squad training sessions taking precedence over Celtic League matches, with Irish provinces (especially Munster and Leinster) occasionally fielding virtual second teams for Celtic League games.
Split into simpler sentences: The IRFU also insisted on International squad training sessions taking precedence over Celtic League matches. A consequence of this was that Irish provinces (especially Munster and Leinster) occasionally fielded virtual second teams for Celtic League games.