Generally we can have a single user with DBA rights to import/export (using imp/exp utilities) data into any tablespace instead of assigning these privileges to every user account.
Suppose you have an oracle user appdba. Grant DBA role to appdba and you can use this user to import data into any tablespace like this:
imp appdba/pwd file=xyz.dmp fromuser=username touser=targetusername
Similarly export:
exp appdba/pwd file=xyz.dmp owner=username
where the owner is the username for which you want to export data