If the library is pre-assigned and there are no extended attributes, the server list in EG should be showing you all the physical tables for that library as long as the appropriate user has ReadMetadata for that library definition. In EG, when you select View / Server List and expand down, do you see the library in question?
A few other things to look at in SAS Management Console. For this, right-click on the library definition and select Properties.
1. On the Assign tab, make sure an application server is selected that the user in question can access. That will be displayed on the right under Assigned Servers. Now that I think about it, the original post may have had this problem... since without an Assigned Server the library would not show up in EG but would show up in DI Studio.
2. On the Options tab, jot down the Libref value shown.
Using the libref from #2 above (e.g., wombat), now go into EG and submit the following code.
libname wombat list;
(where you replace wombat with whatever your libref is)
Make sure this code is submitted on the appropriate server (there's a select server button at the top of the program in EG if you aren't sure). Then look in the log to see if the value of Engine for the library lists META or something else. If the value is META, there may be an autoexec file which is forcing assignment with the Metadata Libname Engine. That's not a bad thing in and of itself, but some of the consequences could be why you're not getting the behavior you expect for the library.