I recollect that friend of mine told me that his father-in-law was stationed in Greenland and was told by R' Moshe (or by someone who asked for him?) that he should go by the closest city with normal times.

I haven't done a whole lot of research on this subject, but off the cuff, perhaps all of these times aren't "real times", but a personal gauge.  According to the Maharsha 26b, even Rabbi Yose b' R' Chanina held of k'neged korbanos tiknun, but Chazal would not have established the tefilos at those times if not for the Avos who fulfilled the pasuk of erev vavoker v'tzaharayim asicha... So it could be that absent the times of chazal, the halacha would revert to 3x/day.  Although the pasuk says specifically evening, morning and afternoon, you may be to say that's lav davka as Tosfos proves that yaakov davened maariv during the day, for Tosfos a proof that the halacha is like R' Yehuda.  Lulei mistafina midivrei Tosfos, I would have said the timing is lav davka and this is how the rabanan who argue w/ R"Y would answer the question.

Krias Shema is a little fuzzier.  Are the zemanim of 3 hours, etc. mideoraysa, or applications of Uvshochb'cha uvkumecha.  In other words, can we say in absence of zemanim, we revert to shechiva and kima of your time zone?  It seems acc. to the opinions above that that wouldn't be the case.