Most of the applications you are referring to are "PPH", Patent Prosecution Highway, cases. There are multiple ways to "get on the highway" but not every country lets an application get on the PPH based on positive action from any other country. The US has PPH in place with many countries. The idea is "work sharing" between patent offices but to assure quality by doing everything over again but from a better starting place. The statistics the USPTO keeps shows PPH applications
have fewer office actions and a much higher allowance rate. However they claim that quality does not suffer because they do an independent search, on top of what has already been done. See two slides from a 2012 USPTO presentation:
For the PCT PPH the allowance rate is about double the average allowance rate and the average number of actions also drops. It takes one action to say "yes" so 1.6 actions means only .6 hear an initial no.
On the other hand the next slide shows that the US examiners are doing something.
A huge point is that this is not just for foreign applicants. If a US applicant files in the US and a PCT, they may get a positive prelim examination report from the PCT while the US case is still in the queue. They can petition the US to accelerate the corresponding US application under PPH.
I have had two applications that had all claims allowed right out of the box -it is a shock. They included a PPH case and a "regular" case. In both instances I was concerned, wondering if I had received a thorough examination and also wondering if I had left something on the table.
Regarding reexamination - reexamination proceedings are all done by a separate group from the initial examiner.
I recommend applicants take yes for an answer and put the patent in their pocket - and seriously consider filing a continuation application that is not accelerated as a safeguard.