Well, all this is quite interesting lol.
My understanding is that HVAC goes in first (then plumbers, and electricians last), since they need the open and unencumbered space to route their duct work, and since electrical and plumbing can literally go through a duct of at least a certain minimum size if no work around is possible.
If the building isn't closed up by the time the HVAC installers are done and the plumbers need to go in, and if for whatever reason its too cold for them to do their work, I'd imagine that they would either have the electricians skipping ahead of the plumbers, or the contractor would just stall the project until glass goes up or the weather warms up. That said, I'm not sure why the plumbers couldn't install pipes in freezing temps so long as they did not connect and turn on the water. I understand this would most likely delay dry walling until spring next year when the water systems can be tested, but this project is already delayed out the ass, so whats new?