Yes, the command tank was used by Brigade commanders, not sure whether sqdn commanders had one. They had an extra 19 set in the front rh sponson, replacing a 75mm ammo rack, with an extra A set aerial in the glacis mount.
The OP was used by the divisional Artillery and had a dummy gun with a 19 set, a 19 HP set and probably other sets for RA nets.
The Rear link had a 19 set HP for longer range comms with Brigade and or Div HQ.
This is all from memory so I stand by to be corrected!