The Mount Wellington Cableway Company (MWCC) is working towards having a cable car operating at the Hobart landmark within three-and-a-half years.

The Wellington Park Management Trust extended the commercial development area on the pinnacle zone by 15 per cent.

The cableway company asked for the change to accommodate their planned design.

Executive director Adrian Bold said the company was now in a position to lodge a development application, but would not say when.

"We have a timeframe and a target opening [for the project] of mid-2019 to be operational, and so we have a window of opportunity," he said.

"We have a roadmap to get us there."

Mr Bold said the proposed summit terminal would sit below the skyline, so as not to be prominent.

"We wanted to make sure that the planning rules for the top of the mountain married up with the public input that we've had over the last four, five years - and that's to ensure that we don't add another manmade pimple to the skyline," he said.

The firm is proposing to run aerial tram cabins with open-air rear balconies, and possibly glass-bottomed floors.

Its plan also includes a visitor centre that would lie just south-east of the existing observation centre.

Mr Bold told ABC 936 Hobart the boundary adjustment was a critical step.

"If we had just gone ahead without this boundary adjustment and submitted a DA for the visitor centre at the top of the mountain... sure, we're pretty confident we could have complied with the planning system, but I don't think too many Tasmanians would have been happy with another pimple on the skylines."

Mt Wellington Cableway Company's impression of the visual impact of its proposed summit development. ( Mt Wellington Cableway Company )

Trust denies decision means support for cable car

The Wellington Park Management Trust has denied the decision to change its management plan implied support for the development.

Trust chair Christine Mucha said it opened the door to a variety of proposals.

"We get roughly 270,000 visitors a year to the top of the mountain," she said.

"By opening up that area, that very small area, it allows the opportunity to put forward proposals.

"It may be a cafe for example, that will be probably better suited and have less implications on the skyline."

Cable car proponents are now expected to lodge formal development applications.

The trust received 550 representations on its proposed amendment to the Pinnacle Zone last year, which included the cable car boundary extension.

The Tasmanian Planning Commission held hearings, and found the trust did not adequately summarise all of the submissions.

A report released by the commission in July said the trust did not adequately respond to community concerns about the plan.

Ms Mucha said the trust went back and looked at all the representations.

Trust thumbed its nose at council: Alderman

Alderman Philip Cocker is one of the Hobart City Council's members of the trust.

He said the council was very disappointed with the decision.

"We believe the trust has repeatedly failed to make the case against the [Mount Wellington] management plan for this amendment," he said.

"We also believe the trust has thumbed its nose at the representations that both the majority of representers [made] and the strong views that the council put to it, and I think the planning commission also found deep flaws in the process that the trust undertook to look at the submissions."

Alderman Cocker said he had deep concerns about how the issue had been handled.

"I think there needs to be a discussion around the future of the trust and its role and the management plan and to look at what went wrong in this process," he said.

"The council needs to have a look at its membership of the trust, it needs to have discussions with the [State Growth] Minister [Matthew Groom] about the future of the trust to ensure that it is actually taking the management plan and protecting Hobart's premier asset."

Alderman Cocker said development at the Springs was the priority for council, rather than the pinnacle, but the cable car proposal still had a long way to travel before it could become reality.

"The council as the landowner will make future decisions about use of the land and in relation to development on the mountain, and we'll do it properly and assess it properly against the management plan so I think we're a long way from that," he said.

"It's not that we hadn't considered them it was that we had grouped them together rather than treating each representation individually in our report to the planning commission."

Developer's wishes prevailing over public's: Greens

Greens leader Cassy O'Connor said some people who felt passionately about the mountain felt they had not been heard.

"The top of the mountain is a public asset and it's being changed for a particular private developer's use," she said.

Cassy O'Connor told ABC Local Radio concerns about the cable car proposal were ignored.

"Is this what 'open for business' actually means under this Government? Where a single developer can get their eye on a public asset and have a statutory authority, which is paid for out of the public purse, dedicate a huge amount of its time to enabling the wishes of that developer?" she asked.

Mr Bold said he had consulted with both the current Liberal Government and the previous Labor government.

"We've been engaging with all stakeholders, including agencies and departments of government," he said.

"There's no secret there.

"I mean, this is going to be one of the most, or the most, popular visitor attraction in the state, so of course we're talking to Government."