A) This high deductible + HSA model can't affect the market unless it's widespread (probably very widespread), something we're not going to see in the USA (well, not any time soon), and:
B) The experience of Singapore's first 5 or so years of the model cannot be considered very useful (I'm assuming that between the writing and publishing time and the lag in available statistics the referenced paper at best covers the period 1984 to '89 or 90): the period is way too short to see a change in behavior and their per-capita GDP increased by 43% (!!!) for '84-90 inclusive (from the IMF, as suggested by Wikipedia: http://www.imf.org/external/pubs/ft/weo/2006/01/data/dbcselm...).
But your points about inelastic demand and information asymmetry are well taken; I in particular don't tend to think of the latter, having an RN for a mother, my pediatrician as my father's hunting primary partner when I started hunting, having seriously studied biology and chemistry, always reading the prescribing info of any drug before taking it, etc. etc. etc.
That said, how widespread is the information asymmetry problem in the US? I don't have any direct or family experience here, we've all stayed pretty much in the confines of GP type physicians with specialists consulted mostly to rule out things. These GP types have never encouraged "unnecessary" stuff ... but they wouldn't economically benefit from it. The specialists are where you'd expect problems, especially from surgeons who have a bias towards fixing problems by cutting anyway.
EDITED: corrected fencepost error.
ADDED: this high deductible + HSA model is intended to address one area of health care demand elasticity: avoiding your GP's office for minor ailments. There are simple sets of rules available for treatment of stuff like upper respiratory infections and gastro-intestinal illness including guidelines on when you should seek medical care.
Canada is often described as a place where everyone goes to the doctor for a sniffle because it's free. US style 3rd party payment is often close to this. If you have to pay the entire amount out of pocket out of your HSA the theory is you'll apply the above, perhaps through a nurse hotline, and only go in (and get exposed to other bugs) when you really need to.
Hmmm, that brings us to American exceptionalism: are we perhaps more likely than many other cultures to first take care of ourselves and family and only go to the doctor when it's really needed?