Sure, just as a few years ago many elevators were using 60-year-old Alcos and SW1s (and some still are). But since the country elevator continues to disappear in the face of shuttle elevators the problem becomes moot.
There’s nothing wrong with using an SD40-2 to switch an elevator except the operating cost can be high if the useage rate is more than infrequent. One of the big problems is power contactors which are not built for rapid duty cycles on a road locomotive. As for clearances and curves, if it will fit a 5161-cube covered hopper it will usually fit an SD40-2 or an SD70MAC (and if it won’t it probably won’t fit any big switch engine), and as for curves, 17 deg. is OK as long as the track has good ties. (The Class I may not let you take its locomotive over it of course.) It isn’t desirable, but it will work. And most grain elevators with that kind of curvature aren’t long for this world.
I have observed that BP/Amoco purchased (not leased) one of the Green Goats that briefly went to CP for service at the former Arco refinery at Cherry Point, WA. Hybrids would seem to be ideal for in-plant service at small-to-medium-size operations.