It is understood that Greg McConville has been appointed to the role of United Firefighters Union ACT branch secretary, which has remained vacant for several months.

Mr McConville will start the job on October 12, arriving during a period of significant uncertainty in ACT Fire and Rescue.

The union fired warning shots earlier this year over a major restructuring of the Emergency Services Agency, dubbed the strategic reform agenda, which will see the reduction of duplication in support areas among the territory's four services; the Ambulance Service, Fire and Rescue, Rural Fire Service, and State Emergency Service.

That strategy would see fire and ambulance deputy chief officers work in new executive roles, governing shared areas common to the four services.

The new positions would report directly to ESA Commissioner Dominic Lane, but then return to operational roles in times of emergency.

Earlier this year the union described that structure as dangerous, and expressed concerns about what it says is a worrying return to structures in place at the time of the 2003 bushfires.

Significant changes are also expected in the ESA's triple-0 communications centre, or ComCen, with a confidential review recommending that firefighters be replaced by civilian call-takers.

In an open letter to Emergency Services Minister Joy Burch in July, the union also warned of concerns about inappropriate interventions in operational decisions during the major fire at the Sydney Building, changes to the Emergencies Act, and the "continual and systematic" reduction in firefighting numbers.

Mr McConville's appointment to the secretary position comes after a short stint by Paul Swain, who was also the former chief officer of ACT Fire and Rescue.

Mr Swain, who has since become the deputy chief of the Northern Territory's fire service, joined the union following a significant dispute with his boss, Mr Lane.

The fire chief lodged a bullying and harassment claim against Mr Lane, which was not found to be substantiated following an independent investigation.

Mr Swain then resigned from his role prematurely, with six months still to serve on his term.

Acting ESA Commissioner Mark Brown congratulated Mr McConville on the appointment in a statement to Fairfax Media last week.

"The Emergency Services Agency looks forward to developing an effective working relationship with Greg McConville, working closely together, as has previously been done with the UFU," he said.

"It's an important relationship and we expect it will continue to be positive and strong.

"The ESA congratulates Greg on his appointment and we look forward to working with him in the future."

The United Firefighters Union is given strength by its long-standing 100 per cent membership among ACT firefighters.

It took the extraordinary step of ending its association with the ACT Labor Party back in 2012. That disassociation occurred after the UFU complained about the practice of cross-crewing, and about safety and staffing issues.

That decision was described by then emergency services minister Simon Corbell as "difficult to understand".