I'm disappointed that all the discussion seems to be operating at a non-quantitative level. ("If there's any chance, we have to try" against "If circulation can't be reestablished on scene, there's essentially no hope".) Presumably there are academic article that make an attempt at this.
People overestimate the efficacy of CPR because they see people in the movies come back to life after 4 chest compressions and a second of mouth-to-mouth. I wonder if that is the sort of thing driving the discussion
Cold temperature and submersion in water are two neat caveats though. They can be viable a lot longer, in part due to the Diving reflex.