well, i know my employer does do extra contributions to the 401k for all in the office. we have a "safe-harbor company match" and a "year-end Employer Match".
one of them is the company matching where i get 4% matching from my company if i put in a minimum of 5% of salary.
the other is like a company pool of money. say the company has $100k profit that is allocated to the 401k plan (i'm not sure of the mechanics of it). if there are 10 employees, all maxing out out their plan, then each gets $10k added. if employee contributions vary (some max it out, some don't), then the $100k is prorated according to the weighted contributions of each employee.