(1) A work group is a group of 10 or more workers constituted as a work group under this Division.
(2) A work group consists of:
(a) all the workers of a particular employer, or of 2 or more employers; or
(b) all the workers of a particular employer, or of 2 or more employers, at a particular workplace.
(c) a particular class of workers of a particular employer, or of 2 or more employers; or
(d) a particular class of workers of a particular employer, or of 2 or more employers, at a particular workplace.
(3) The same worker cannot simultaneously be a member of 2 or more different workgroups.
(4) The workers of a small employer cannot be members of a workgroup unless the employer agrees.