Until there is a legal affidavit requesting information, you are under no obligation to share any employee data.
It is not uncommon for ICBC to try and assess a person’s salary, mobility, and tenure for settlement purposes. For example, they may ask if an older employee had mentioned retirement; they may ask if the employee was on track to become a manager.
It’s recommended that you contact the employee and let them know what ICBC is requesting, if the employee approves the information being shared, then it is moot; but the employee’s legal counsel may have other plans/ideas. Otherwise, treat the request like you would a background check and share only necessary information (worked how long, title, responsibilities).