Okay, looks like the game is not differentiating it then
Only way to find out then is maybe mapId + player position on it if mapId is a special one. If for example mapId = IC district mapId 1 and the position on x or y axis is above a value, then you are in the base. But if the pos. values are below a value, you are outside the base next to the door.
Else I don't know what could be used here if there is not other API returning some "IsInBase" stuff.
Other idea as event trackes do that: Could you maybe check for the mapPins of the base vendor's that do not show outside of the bases?