Found this on the WEB. Don't know the difference between mainline trains and yard switching trains.
Do any railroads still use cabooses?
So, do railroads still use cabooses? Yes. Cabooses are no longer used on mainline trains, however, they are still used during yard switching. In the early eighties, the caboose was replaced with a device called the end of train device (EOT; see derf link) on mainline trains.
Do Trains Still Use Cabooses? | Worldwide Rails