But for the sake of the scenario and to be able to fcous on priorities, let's say that some group or groups decided to follow their own plans by leaving the building , or calling other from other buildings to join or whatever.
Then what ?
I think for myself if someone decided to leave I won't care. But if someone is calling others whom I don't know, I would be careful not to reveal everyuthing I have stashed in the building for my own survival. I do have a small stash of food/drink/tools that will not support many people.
About fire, it is not that critical in our office building. It is a modern building but we have some spacious "balconies" and some metal waste baskets that so appropraitely are used for "paper recycling". They will be already full of waste paper ready for burining. We can use for fire if we had to cook, though unlikely. But who knows we may need to boil water for sterilization.
Let's think about the scenario for a minute - its a blizzard, which is a short term event, you're not the Donner Party. Your small stash of food/drink etc might as well go into the pot to help everyone, it won't make any direct difference to your survival. And calling more people into your area is fine, better you know they're there and they're okay than to have others separate from your party and doing not as well - bodies = heat. The rest is waste management.
If someone chooses to leave the building against your advice, you take their names for the record, where they're headed, and make sure they leave with a list of those who remain behind, an emergency contact for each one, and what their status is (all ok, cold, low food, 2 diabetics). Ask them to contact authorities to send help, and to let family members know. Then you sing their death songs, and hope they get through. You're not lost in the Andes either, you're probably in an office park, one of you has a misconception about how far and how tough it will be to walk out to safety. They may end up as popsicles, or they may be heroes around the water cooler the next week when things are back to normal, for bringing you help. It doesn't matter - if you've decided to stay put and keep people warm safe and calm until the storm blows over, that's how you assess the situation, its your brand of heroism. Your best argument against people going off on their own is to wait for the storm to die down - they're best argument may be 'if we wait, [Carol from Accounting] may go into a diabetic coma.' Without some proximate danger to one or more in your group, the best course is to wait for better weather, and you appeal to folks on that basis. You may be cold and uncomfortable for 48 hours, but most often no one is going to die simply by staying put.
I would just repeat the earlier warning against starting any kind of fire in an office building. I don't believe it will be necessary, and if it was you really don't want to deal with the smoke in return for the heat you would get from a paper fire. Closing doors and moving to an interior space will retain more heat than you could possibly generate from a fire indoors.