I've been curious as to why there aren't really any diesel-electric hybrids from any major manufacturers (that I'm aware of). I think two significant reasons might be: 1) the significantly greater amount of power necessary to start a diesel (because of the higher compression ratio) as compared to a gasoline engine (although this still shouldn't be an issue if the engine is equipped with a large starter/generator); and, 2) the fact that gasoline engines are in some respects better at efficiently handling temperature changes from start/stop operation.