How do you find the COBRA health care costs of current employer?

Let's say you are an employee at Yahoo and have a great health care insurance plan, but you are afraid of having a COBRA qualified event (like many other employees have had recently) and want to know how much your COBRA health care insurance plan is.

How can you find this amount out? A friend of mine at Yahoo tried to contact her insurance carrier and HR department anonymously, but they wouldn't tell her. Is there a legal requirement that companies should be forced to disclose this info to current employees?