I don't know about today, but when the C&TS was just starting out 30 years ago there was no way to turn an engine (or anything bigger than a speeder) in Antonito so anything that needed to be turned would be hauled out to Lava and turned there.
Now days, I don't believe it's been used for anything other than as a place to stash the OY's water car when the Eureka came to visit. The Eureka needed water at Lava and since the tank there is out of commission, they brought out the water car to supply it.
Don