CB40 winners Hampshire will take on predecessors Surrey in the group stages of the 2013 competition.
Group B will also feature Lancashire, semi-finalists this season, Durham, Derbyshire, Essex and Scotland.
Warwickshire, runners-up at Lord's, were drawn in Group A along with local rivals Worcestershire and Sussex, the other side in this season's last four.
The winners of the three groups and the best second-placed team will qualify for the semi-finals.
Kent, Netherlands, Northants, Notts, Sussex, Warwickshire, Worcestershire.
Lancashire, Derbyshire, Durham, Essex, Hampshire, Scotland, Surrey.
Glamorgan, Gloucestershire, Leicestershire, Middlesex, Somerset, Unicorns, Yorkshire.