Right. What I was getting at is that the blurb and accompanying article seems to almost imply that through some magic and a fuel cell the plane could move itself without some means of motive power. Currently this comes from the jet engine and that's it (barring, of course, external sources like a tug). Adding that motive power would add weight. Other non-sexy things might include some sort of chain embedded in the taxi way that could grab onto the front wheel of the plane, similar to the systems that bring a car through a car wash. The tug could get the plane out to this system and pull it along until it got to where it needed to go. Given that this is a system that would be in one place, and likely using electric power, you could generate those electrons in whatever eco-friendly way you wanted. Of course, this also hand-waves about a billion engineering difficulties away, as well -- chain strength, debris getting in, weather, etc. And then you could use the hand waving to extend the idea to use a catapult system to launch your commercial jet, just like an aircraft carrier
Your point about operating temperature is also a good one. Given that you want the engine making the most power at takeoff, running up a cold engine may not be a fantastic idea. I'm guessing for this use case of frequent short flights that this airline has, the engine is likely up to operating temperature more quickly. For long haul flights, time on the ground will shrink and be dominated by flight time.