"This is a far bigger response than any country has achieved so far (and it's extra difficult because the at-risk groups are probably the most dependent on external aid, as well as already lacking social contact)"

How have they achieved this? What concrete measures?

They haven't yet (no-one has). The point is they are recognising that such measures are very hard on people, and so they don't think they can stay in force indefinitely.

Well, if I try hard to imagine how they think, without assuming incompetence, it would be as follows:

Assumption 1: Our country will not be able to take measures that are extreme enough to stop exponential growth. Assumption 2: Once a certain level is reached, we can drastically lower the doubling time so that the number of simultanious cases are kept below what our healthcare system can handle. Assumption 3: If we stay below the level that the healthcare system can handle, mortality rates will be low, maybe lower than 1%. Assumption 4: The total number of individuals that will require hospitalization is low enough that the healthcare system can treat all patients needing treatment in a few months.

If assumptions 2 is not met, the mortality rates of pations that require treatment is likely to be similar to what is seen in Italy, ie roughly 15%.

If assumption 3 is wrong, and the real mortality rate is about 3-5%, having about half the population infected, will still lead to huge numbers of dead, more than the population is likely to accept.

If assumption 4 is wrong. Italy is currently unable to handle 20000 cases. A country like the UK may be able to handle maybe 10000-20000 simultaneusly. If 10% of the population requires hospitalization, and each patient will stay there an average of 1 month, measures will have to be dragged out over several years, anyway.

Assumption 5: This only needs to be done once, meaning there will not be second or third waves or mutaded viruses that will need to spread in a similar fashion in the same time period.

At some point, I think every country will realize that they need to take drastic measures, enough to stop the spread from being exponential. Doing that after detecting 100000 cases is VERY different from doing it after detecting 1000.

The downside, of course, of preventing exponential growth, is that most measures will have to be kept in place until there is a vaccine or other cure, and that could take 2 years.

The growth will always be exponential. What you can change is the exponent. I don't think they are crazy for suggesting that extreme measures are unsustainable and their use should be timed correctly. I'm not completely sure they're right, but neither am I sure that extreme measures are right. Keeping a quarantine on a whole country up for 2 years seems unlikely. As I understand it, this plan hasn't just been hastily put together overnight, a team has spent a while researching and modelling outbreaks in preperation for just such a scenario, and as such I am inclined to trust them more than politicians (who are always happy to be seen to be doing something about a problem) and laypeople on the internet.

Growth does NOT have to be exponential (or at least not with any near-constant exponent). Furthermore, if the doubling rate is half a year or more, it really does not matter that much if it exponential, unless the number of already infected is already huge, since a vaccine is likely to come within 2 years.

From my perspective, it appears that politicians do NOT want to take sufficiently drastic measures, as the economic consequences will be huge (let's assume that Spain and Italy will keep or increase the measures they already have for 2 years), and so far, their measures do not seem to be sufficient.