What is the impact of hybrid vehicles on greenhouse gas emissions if they were to be used as emergency vehicles?

Several weeks ago I was trapped during a snow storm and accident just south of Ottawa, Ontario returning from Quebec City, Quebec, for 3.5 hours. I was driving a 4 wheel drive hybrid Tahoe. If the average vehicle in the long, long line was getting 20 miles/gallon, at an equivalent fuel consumption of 2 min per equivalent mile, it would use 5.25 gallons of gasoline to remain on and keep the occupants warm. That would be 102 lbs CO2 per vehicle. I was able to keep the heat on, plug into a 120V outlet with my laptop and broadband card, and watch a DVD with a total usage of less than 1 gallon of gas or <19.4 lbs CO2.

The national average for county vehicles is 7 hours idling per week, or 364 hours per year. If we assume the same average as above (generous as most emergency vehicles use larger powerplants with an average of 14 - 16 mpg) the idle time would be an equivalent of 546 gallons per vehicle, or 10,600 lbs CO2. The primary reasons for leaving most emergency vehicles operating idle is that on-board computerized equipment and hydraulics (police, ambulance and fire) require power.

The heavy hybrid vehicles produced by GM and Ford provide the ability to power such equipment while cycling the engine only to recharge the batteries. Using the experience cited above (3.5 hours/gallon), the reduction would be to 104 gallons, or 2,000 lbs CO2, a savings of 442 gallons ($972 in idling fuel costs at $2.20/gal) and 8,600 lbs of CO2 per vehicle per year in idling alone. The numbers I am using are rudementary, but you get the idea.

Thoughts?