Had a look around and it’s not totally clear but it looks like the Faroes tunnels are mainly funded by pretty high tolls - would those be accepted in Scotland considering the history of the Skye Bridge?
The problem with the Skye Bridge was that the Tory government of the day had paid very little attention to the facts on the ground. It wasn't known by locals that the Kyle-Kyleakin service was very profitable for CalMac, and many locals on both sides were informally allowed to travel for free, especially if they could speak Gaelic to the crew.
Had the bridge been built as an ordinary public project, tolls would probably have been no more than a pound, which wouldn't have attracted any hostility at all. To charge £5.40 was a complete disgrace, and the failure to implement a Skye+Lochalsh toll as part of the PFI agreement was something that the locals never forgave. The discounted tickets did come later, but the damage had been done. It didn't help that people were getting prosecuted for blocking the toll booth, which was completely out of order and caused even more resentment among the islanders.
The high tolls wouldn't be a problem in itself if the financing was clear. It would need a full and honest discussion with the communities about what it will actually cost, but I don't think there would be any hostility to a tolling system that was operated in the same way that the Norwegian or Danish tolls are. There, the tolls are removed once the bridge or tunnel is paid off, and it's already happened that some tolls were paid off far quicker than expected, such as at the Nordkapp tunnel. In the Faroes, the situation is a bit more complicated: the politicians can't decide whether to make the tunnels toll-free now that the investments have been paid off, to keep a limited toll to pay for infrastructure, or to keep them the same and use the money for other road investments.
Having said that, at least two of the Faroese tunnels have had their price reduced progressively as they were paid off.
£100m for a near 11km undersea tunnel sounds a bit cheap - would you be allowed to build that as a single bore two way tunnel in this country?
From what I understand, the Faroese tunnels aren't compliant with the relevant EU Directive, which probably explains why they were able to build it a bit cheaper than elsewhere. Having said that, I believe that the Mont Blanc solution, where the area underneath the roadway was transformed into an escape route that utilises small rescue vehicles is perfectly acceptable and complies with the Directive. There's no need for a separate bore or parallel escape tunnel, and this system would be perfectly fine for rural tunnels with low amounts of vehicles daily.