That (re-paving 20-30 meters of a walkway) is a tiny project, it has nothing to do with the complexities of large projects (which are the theme of the article).
On these tiny projects, usually the difference between what a public administration and a private can do is only the bureaucracy involved which is a lot for the public and very little for a private firm.
Others have mentioned this already but there are plenty of regulations that are relevant just for hospitals because of what they are. For example, the bulk of the historic LA county hospital is vacant, because the building is no longer up to the seismic standards required by the state for a hospital. When you have a big earthquake, you probably want the hospital to be the very last building to fall in the city. The building, however, is used for things like offices or storage because these uses don't have the same standards as a hospital.
It is very difficult to compare different (complex) projects (independently from whether they are public or private) because - Captain Obvious speaking now - they are different (not only the actual thing that is built, also the quality of the project and its engineering, the chosen contractor and a lot of other factors come into play, your new examples add two completely different countries and two completely different periods of construction).
Construction times are even trickier, as they may also be influenced by other factors (authorizations/approvals or changing norms as an example).
A (typical) appropriate construction time for a (large/complex) project is around 4-5-6 years, 3 years means they were fast (in Chicago , in the '70's) 10 years means they were slow (in Slovenia, in more recent years), but otherwise there is no way to make senceful comparisons.
It can also depend on the depth of the bureaucracy; in my little town the town owns a pothole/miniature paving setup, and fixes their own minor things; they don't have to contract out with a company to get it done.
A (larger) town nearby they contract, and everything gets pretty bad before they sign a huge contract, and the company works for a year and fixes everything in one long go.
On these tiny projects, usually the difference between what a public administration and a private can do is only the bureaucracy involved which is a lot for the public and very little for a private firm.