Employees in high salary groups can opt to get a "NetzCard" which allows unlimited travel in all DB operated trains. High management gets a real BahnCard 100 for them and a second person.

The free day tickets for private use that every employee gets are limited to 16 a year (but only one a month is tax free) and don't allow to take someone with you.

By the way, not every employee can use first class for business related travel (many can).