Doc confirmed the two proposals had been "approved in principle" and provided Unesco with copies of impact studies and proposed mitigation measures.
Unesco's World Heritage Centre and the International Union for the Conservation of Nature, an international environmental group, were assessing the information.
The next step could be the preparation of a report to be considered at the next World Heritage Committee session, in June or July next year.
From that meeting, officials could be asked to visit the area to assess the impact of the proposals.
"The World Heritage Centre has requested the New Zealand authorities keep it informed of any development, including the outcome of the public hearings," Ms Williams said.
Late last year, Conservation Minister Kate Wilkinson announced her intention to grant concession applications to both companies. Submissions were then called for and were heard over several weeks this year by a Doc hearings panel in Queenstown and Te Anau.
Doc media adviser Reuben Williams said yesterday Unesco had no legal jurisdiction over the concession applications process.
Unesco was interested in world heritage but "they won't be in a position to be involved ... in the decision making".
Doc was still preparing reports on the applications to be forwarded to the delegated decision-maker, Doc operations deputy director Sue Cosford, he said.
"No formal decisions have been made ... it could be some time off."
Milford Dart Ltd director Michael Sleigh said he "just can't see how" the 11.3km tunnel could jeopardise the World Heritage Status. It would have a "minimal impact" compared with other developments at Milford Sound.
"If they [Unesco] were coming, they should be having a very close look at what the various Te Anau-based stakeholder groups [in] the Milford village [have done] in terms of the 6ha of native forest they removed to allow for commercial expansion.
"It's far more dramatic than anything we're proposing.
"They should also be talking to the people at Gunn's Camp and the mayor about recent support for the Haast-Hollyford highway and what impact that will have on the World Heritage status."
Riverstone Holdings Ltd director John Beattie said Unesco would be "absolutely satisfied" with his company's project, which would be an "exemplar for future activities inside the Department of Conservation estate in New Zealand".
He likened the project to the 7.4km Kuranda Scenic Railway which traversed native rain forest in Cairns.
"I'm advised by the operators ... that the benefit, they believe, of the infrastructure to the World Heritage status position - the knowledge and understanding of the rain forest - has been considerably improved ... as a result of the infrastructure being in place.
"We expect the monorail will be no different in that regard and we'd expect, having been through a detailed eight-year process, which has been extremely robust, with Doc ... that Unesco will respect the integrity of the Doc process and this will cease to be an issue."
Unesco World Heritage sites:
*962 sites worldwide, including three in New Zealand.
*Te Wahipounamu ("Place of Greenstone") covers the Aoraki/Mt Cook, Fiordland, Mt Aspiring and Westland National Parks; included in 1990.
*Tongariro National Park included in 1990, New Zealand Subantarctic Islands in 1998.
*To be included, sites must be of "outstanding universal value".
The proposals:
*Dart Passage Tunnel: An 11.6km, commercial bus tunnel from the Routeburn road in the Mt Aspiring National Park to the Hollyford road in the Fiordland National Park. Cost: $150m.
*Fiordland Link Experience: A catamaran trip across Lake Wakatipu to Mt Nicholas, an all terrain vehicle trip to the Kiwi Burn, then a 43km monorail journey to Te Anau Downs, on Lake Te Anau. Cost: $175m.
