So they are going to do a heat treatment to kill even the dormant bugs hiding in the walls and such.* My question is: If we have a professional come out, and treat for bed bugs, would we then be free to rent out to tenants after waiting the two-week period recommended by the extermination company?

The wind getting into the crawl spaces and freezing the pipes if it's not properly heated can be costly. 

The issues they faced from bursting water lines, heating units failing, extreme wear/tear on roofs etc.  

If the basement is fully finished and a livable, heated and cooled space, with egress and minimum ceiling heights, it would be counted as part of total square footage of the house.

She included garbage removal, plowing snow in the driveway, utilities and heat.

Many are on boiler heat. 

There is no heat and air back there.

Additionally, the hardware stores in the area are sold out of pipe insulation and heating tape so I'm not sure what else I would even do if I were close by aside from trying to thaw it with a blow dryer. 

That is indeed considered an "appliance" i.e. 1245 property and eligible for bonus and S179.Oil tank might be part of the HVAC subsystem and thus part of the building if the oil is used for a heating furnace and if the tank is connected to the furnace/building. 

We are happy to keep helping our landlord with this, but running 3 space heaters for long periods of time is adding to our heating bill.