One other option to avoid 24hr a day idling for engines that are used sporadically in cold weather is a Kim Hot Start heater system. As of about 5 years ago I think one could be purchased for around 10K plus installation. As I understand it they electrically heat both the coolant like any automotive engine heater but also the motor oil. The down side is that the engine has to be parked next to it's dedicated power outlet. I assume it requires a pretty large circuit. Dan R., this option was discussed for the shortline I presume you are referring to back when the power was the GP35's. I thought it was a good option provided a power hook up could be provided at the several locations on line. I think this was the big problem more than the cost of heating units.
I have been blessed in recent years to have gotten hands on experience working on steam and operating steam at SVRy. I am as enthralled by it as any foamer out there. To diss diesels simply because they displaced steam is ignoring the reality of progress which is inevitable. If one could turn back the clock to have steam running would be to also embrace many of the less desirable aspects of life many decades ago before advances occurred in medical science and a host of other things we now take for granted that make our lives a heck of a lot easier than tohose of our grandparents. That's living in the past. So being what I consider a realist, I enjoy well watching trackside in the Blue Mtns. as the diesel units of a UP freight struggle by upgrade in run 8. What interests me is the technology that makes a diesel locomotive function. Steam technology is equally interesting to be sure, but if one has the opportunity to get a little sweat equity working on say an elderly GP7, you'll know what I'm saying. There is an amazing amount of fine design work that went into building one of these old beasts let a lone a modern one. My hat is off to the engineers that designed them. Indeed some diesels seem to have more endearing qualities than others. I enjoyed a short ride in the cab of an Alco RS3 once. The engineer walked me through the procedure of starting it, so I could get a better appreciation. It was pretty cool.
As to the SVRR 110 Plymouth Critter, about the only redeaming quality it has is it's utility. I've ran it many trips doing fire patrol, switching and even ran it pulling 2 pass. cars to Sumpter on a couple trips. It's not a lot of fun to operate, but it sure has been a work horse. It will be nice to see it retired and possibly made into a boat anchor.....