I suspect that some new commute/passenger locos will be gensets. If somebody's getting one with 2 Cat engines instead of a 710 that can't meet Tier 4 then a genset arrangement seems very probable (recent post complaining about that). Hasn't happened yet because passenger equipment gets bought so seldom, and unless forced otherwise a fleet will usually try to keep everything using at least the same engine family for parts & service reasons.

On the non-train subjects, I'm going to put on my caveman hat too. MTBE was a true gift to the refiners when oxygenation became mandatory (it did really help when we were running old cars in the wintertime, especially reducing carbon monoxide) because it was a waste product otherwise, improved octane a tad, provided the oxygen, and mixed well at the refinery. Unfortunately, it was a water quality nightmare. Ugh. When we figured out what was going on the ethanol folk cam around.

So now we use ethanol as an oxygenate in the wintertime and to feed the corn lobby year-round (only corn-based ethanol is acceptable - punitive taxes and other rules prevent ethanol from other sources). Everything said above about it being wrong is correct, plus: it messes with older plastic/fiberglass gas tanks causing leakage, it has to be mixed at the distributor not the refinery, and it actually increases emissions unless extremely fancy (read $$$$) feedstock is used to compensate. And if you get more than 10% in the gas it wrecks fuel systems that aren't specifically designed for it (so if you don't have one of those "flex fuel" things you WILL have problems and breakdowns with 15% ethanol which is now legal and arguably required because people were buying less gas so the corn ethanol folk weren't making as much money). Most CA refiners long ago said, and ARB agreed, that they could easily and more cheaply meet the state's fancy fuel standards without ethanol, and with modern vehicle emission systems the oxygenate has no benefit anyway - it was mainly aimed at all those carbureted things running around in the 80s and 90s. Ethanol is a gift to the corn folk, not a real emission or even GHG improver. OTOH, it does produce lots of tank trains...