Gave this scenario another go today. Having dropped-off the Spetsnaz and attacked the base, I steered to the minelaying area and, this time, found the box on the Mission screen that allows you to set the activation times for the mines (really helps when you're looking for it)!. Set it to ten hours and started sowing, dodging the annoying minesweeper as needed.
While I was focused on this, the Spetsnaz took it on themselves to return to the airbase and attack it again with small arms, drawing the patrol back on their tail. Doctrine was set to Weapons Tight and couldn't be overridden to Weapons Hold. Managed to escape after the Spetsnaz had exhausted their ammo and came back under control, but the flow of intel to the sub was hindered in the process.
In the end, I laid 22 of 24 mines. By now, it was getting tight if I was going to reach the Safe Zone before the scenario ended. You essentially have no control over the minelaying, which proceeds according to parameters known only to the AI. Suspect it has to do with proximity to other mines already laid. After a while, it becomes very hard to find any legitimate locations for your remaining mines. The sub moves at random and quickly countermands any instructions you give it. Eventually, I ran out of patience and tried to reach the Safe Zone with two eggs unlaid.
Despite a couple of sonobuoys out to sea, I encountered no opposition. However, it was soon obvious that I wasn't going to get there on battery power and would have to go to periscope depth to recharge at the halfway mark. Accepted this and continued. Unfortunately, playing at Turbo speed to offset the boredom, I was tripped-up by the AI repeatedly re-setting my speed to creep or even full stop. As a result, I ended the scenario just outside the Safe Zone.
So, I successfully landed the Spetsnaz, who carried-out their attack, laid 22 of 24 mines in the harbour approaches and got away without losses. Nevertheless, in game terms, it was still a Minor Defeat with a score of 250.
It's an unusual scenario and a bit of an experiment, but it really doesn't work for me. The minelaying is slow, tedious and heavily dependent on random factors. Improved player control is needed (a 'Lay Mine' command, perhaps) and the scenario briefing should highlight the Mine Activation box on the Mission screen. With this improvement, there would be a chance of making it to the Safe Zone in time. Not sure what caused the auto-correction of my speeds on the way out, but it might have had to do with reverting to a default of 'creep' at the end of each movement stage (if you try to steer straight for the Safe Zone, you are given a dangerous course near the sonobuoys, so you have to do it manually in stages). In any event, I found the scenario more annoying than entertaining and can't recommend playing it as matters stand.