Sorry if I missed the other ?. As a practical matter, if the pipes are fully evacuated of water, no antifreeze is required. In the same line of thought - if the pipes are not fully evacuated, but run below the frost line, no antifreeze is required. In the real world, it's a good idea to add antifreeze to lines when possible (water clings to pipe surfaces and will eventually find it's lowest level, so having the AF in there can prevent some co$tly problems). How deep a freeze you are likely to encounter depends upon your latitude (mostly), on the bottle it should say the freeze/ burst protection based on % AF to water. So guestimate how much water may be left in the line and add enough AF to compensate for the 'worst case scenario' (Ma Nature provides a record breaking freeze).
With so many people in so many climates here, that's about the best I can do - but keep in mind, the better (more thoroughly) you blow out the lines, the better chance they have of surviving the winter 'in tact'.