New CB40 holders Surrey have been drawn against runners-up Somerset and semi-finalists Durham in the group stages of the 2012 competition.
The tough-looking Group B also features Nottinghamshire, Hampshire, Scotland and Glamorgan, who have been re-branded as Welsh Dragons.
This year's other semi-finalists, Sussex, are in Group C.
The winners of the three groups and the best second-placed team will qualify for the semi-finals.
Netherlands, Leicestershire, Worcestershire, Lancashire, Middlesex, Essex, Gloucestershire.
Scotland, Durham, Hampshire, Surrey, Glamorgan, Somerset, Nottinghamshire.
Unicorns, Derbyshire, Yorkshire, Kent, Warwickshire, Sussex, Northants.