No, to get access definitely to a base you have 2 ways :
-get membership.
-get FRIEND status in database then be led once in the base (you get a message saying you now see the location).
a friended character loses location once he is killed on site.
Though there was a bug that made some bases visible to other characters. It happened to me last era. Maybe it has to do with the names that were added.
There is also another way.
Someone already member of a faction can tag someone buying a base, he will then see the base, but will not be member or friend, never being registered anywhere in the terminal, a ghost in the system.