Guinea has a strong policy to not be just a quarry, the want value adding jobs. Having the port in their country creates more local jobs and avoids political risk.
Also don't forget about Guineas other railways hauling bauxite. This is the one the company I work for owns.
The factsheet report is very positive. Pity that Australia doesn't do more down stream processing.
According to https://en.wikipedia.org/wiki/Railway_stations_in_Guinea the Boke railway is standard gauge.
Because the water near the shore is shallow, barges are needed to transfer the ore to capesize vessels 40km off shore. This is like to proposed barges at Port Augusta which is also shallow.
There are a number of bauxite mines, Rio I believe may have one as well.
When EGA first bought the lease off BHP, one of the stumbling blocks by the local govt was they wanted down stream processing such as an alumina refinery. Realistically this isn't going to happen any time soon as the population isn't ready for it. You'd spend $5B to build a plant, mostly run by well paid expats who live in an effective community island (prison) and make almost no significant financial contribution to the local economy and just send all their money home.
The work we had to do just to bring the local people up to a suitable standard to run a basic open cut shallow quarry and run a railway was huge. Realistically you are dealing with people that have yet to join the 20th century with grossly inadequate education and general life skills. We had dozens at a time in training in Dubai at a time teaching them the equivalent of high school and how to operate machinery.
In country we had to provide everything, there was nothing of use to us, including water supply, power supply, railway, port, roads....
From the start we stated a zero bribery policy with the govt which initially thought this was just lip service until they realised it wasn't. The only thing we provide free is water. Hence the locals call us the Water company. Our company home page is called "MyEGA", which in the Guinea local language means "Hello" or similar, fortunately not anything else.
Anyway, so they have a bauxite mine where we add as much value into the country as possible, but I doubt the alumina refinery will be built this side of 2030 or at all. The bauxite is being used to supply our Refinery in the UAE which will likely be expanded. The bulk of the rest of our alumina comes from ALCOA WA, which is good stuff and we have longterm contract.
While Australia does export some bauxite, mostly from Wepia and in recent years Gove after the not very old Refinery was closed due to high energy costs, most is converted to alumina in Australia, however a decreasing amount is then smelted to metal in Australia.
Personally I would limit bauxite exports to 10% of mined and alumina exports to 25% with the aim to increase metal production in country, not reduce alumina production.
Unfortunately govt policy is not longer supporting such onshoring.