Shamrock Rovers A were the champions while the runners up, Salthill Devon, were promoted to the First Division.
The six non-reserve teams included Salthill Devon and Tullamore Town, both of whom played in the 2008 season.
Carlow and Tralee Dynamos were making their debut at senior national level.
They were the first clubs from their respective counties of Mayo, Carlow and Kerry to play at this level.
However they were subsequently promoted directly to the 2010 First Division after their opponents, Kildare County, withdrew from the League of Ireland before the play-off could be played.