For processes where the process_type_code is PLSQL, the actual code can be found in the process_source field.
Its a CLOB, so you will need to use DBMS_LOB.instr to query it.
SELECT * FROM APEX_APPLICATION_PAGE_PROC
WHERE process_type_code = 'PLSQL'
AND DBMS_LOB.INSTR(process_source, 'MY_TAB') > 0
Don't forget that it is case sensitive.
Yes it is