The reason it's cheaper is because the demand is lower. Since you can't (easily) store electricity, they actually shut down the generation facilities. If demand spikes, they bring it back ("dispatch" in the parlance), and this marginal cost of dispatch can be significant. The predictability of demand is used quite a bit for maintenance cycles, but it's not the only item on my list of impacts ...
> Electrified bus lines are a simple, old technology and yet
> cities burn huge amounts of diesel moving people around by
> bus.
Don't forget they also burn huge amounts of fossil fuels to produce the electricity!
My humble city (Berkeley) recently switched 200 city trucks to biodeisel but is switching back due to (ahem) technical problems: some bacteria mold was killing the trucks.
Ah, technical problems all around us! Despite having the political will, Berkeley is back in the greenhouse gas business.
/jordan