I answered this a little bit here: https://github.com/bitovi/canjs/issues/931
Short answer, do not use can/map/list. It will be gone or replaced in 3.0. Something similar might happen to can/map/sort, but that is much less likely to disappear (more likely to be moved with a slightly different API).
Anything that is not documented you should avoid or help us add docs so it is officially supported.
Long answer, we should have removed this and other plugins in 2.0, but as we provide semantic versioning, we aren't going to remove them until 3.0 because they are still "documented" in that they are on our website (in the downloads page).
can.Map and can.List used to be in can/observe and called can.Observe and can.Observe.List. The can/observe/list plugin added things to the base can/observe/list like filtering.
When we split can/observe into can/list and can/map, to maintain "steal" compatability, can/observe/list became can/map/list. This is so we could alias every plugin that was under can/observe to can/map.
Basically, these things should have happened for 2.0, but are lingering until 3.0.