https://www.up.com/aboutup/community/inside_track/hybrid-locomotive-pilot-it-250530.htm
After a successful trial UP is expanding use of hybrid diesel locomotives for yard work. They can run on batteries and batteries can charge while diesel is running. They can reduce fuel consumption by 80%.
They are made by ZTR a Canadian firm that appears to be a partnership of a group of smaller companies. https://www.ztr.com/about