Work Train at West Farms Square

I drove by W. Farms Square/E. Tremont Ave on the 2 and 5 line and i saw a work train today sitting north of the station. It had one rider car, one tonner locomotive and a work flat. Does anyone have any clue which loco and rider this would have been? I am not familiar with the positioning of this equipment on the line not being from NYC.

Work trains generally consist of various NYCT diesels (mostly GE switchers) along with R33 rider cars (R161 rebuilds).