The CTA has two small diesel switchers - no bigger than a GE 44 tonner - kept at the lower 63rd yard and used for M-O-W purposes and for shuffling cars around the yard there. One was purchased from an industrial outfit around Lockport or Morris and turned out to be unsuitable for the task and sits there but unused, so another similar diesel switcher acquired elsewhere does the work. I'm almost positive I saw it with a train of M-O-W ballast hoppers sitting in a middle track on the Congress branch of the Blue Line, so if that's the case, it can venture pretty far out of the lower 63rd yard without physical restrictions. (Both of these locomotives were within view when IRM's Snowflake Special charter ventured into lower 63rd earlier this year.)
Aside from the current fleet of diesels, the last two electric locomotives the CTA had were S-104 and S-105, which were used to handle freight cars on the north side main before that service was discontinued in the 1970s. These were yellow steeplecabs built with components identical to those found in 4000-series "L" cars. The S-104 is owned privately and stored on a siding in Michigan City (I believe I've heard Tadman refer to this as the "secret steeplecab"). The S-105 was at East Troy for a while, and is now at IRM and being worked on in the diesel shop (barn 2).
That old car might be worth money!