I found this info on Google Product search
for the 500:
Min Operating Temperature 41 °F
Max Operating Temperature 95 °F
Which I think translates to minimum of 5 degrees celsius, just above freezing.
I couldn't find other specs but I doubt these have changed much in the 505 and the 700, anyone care to look it up in the actual Sony manual? Because I suddenly don't feel like taking my Sony out in subzero temperatures.