RMT has declared as dispute with LU over its plan to unilaterally move some workers out of the TubeLines collective bargaining structures and reallocate them to the "MATS" function of the LU collective bargaining machinery. One of the effects is that these workers are no longer formally represented by the reps they elected to represent them.
The issue may seem obscure, especially to non-TubeLines staff, but there are vital principles involved here.
"Machineries of negotiation", the structures via which official negotiation between unions and the employer are conducted, have to be agreed by both parties. TubeLines has its own machinery, a legacy of its history as a seperate entity prior to the reintegration of TubeLines work, and staff, into LU. Changes to the machineries, including which workers are covered by which bit, have to be negotiated and agreed, not imposed.
LU has form here; in 2017 it unilaterally abolished 12 rep positions on LU stations. Although RMT declared a dispute, the fight was not pursued as vigorously as it might have been. That lesson should be learnt here. We can't allow bosses to ignore agreements.