The problem could still occur but you would have to be capturing all the queries to your internal LLM systems and then using that data for training. You have complete control of the model so you could just choose not to do that and I would think data leaks of this nature would be less of a concern for an internal environment anyway. You would know that only authorized individuals would have access to the data. I suppose there could still be a very small chance of leaking data to unauthorized employees, but if a rogue employee wants to access data they should not have access to fishing an LLM would probably be the least productive way to do that. Your access logs for the LLM system would clearly display the attempts.

Some commercial services are starting to offer "Enterprise" licenses that prohibit the collection and use for training of your data and that would address the concern as well.