Without knowing a lot more about the case and the documents in question, it is impossible to tell whether the company has a right to withhold them from production pursuant to the subpoena. There is no such thing as a "professional privilege," but there are many other privileges that might apply.
You should ask for a list of documents that were withheld from the subpoena, and then decide if those documents are privileged. You may need to apply to the court for compliance with the subpoena if documents are improperly withheld.
Document in the file that were written for the purpose of preparing a defense to your action are protected. Many times, injury reports, investigation reports will, employee interviews, etc. will not be subject to a SDT.