I would rather they not provide the documents that I produce to their client, though I am not sure that there is anything I can do about it. Is it possible they will give it to their client?
Lawsuit / Dispute Attorney
I think it is normal course to give a client access to documents produced by someone else in litigation.
The only way to prevent it is to obtain a protective order so that the documents are "attorney's eyes only." While these are often issued in order to prevent trade secrets from falling into the hands of competitors, my experience is that judges are reluctant to issue them absent very good reasons to do so.