This seems to be growing more common. In just the past couple of months, I have heard of two other employers who are offering pet insurance to employees.
From what I have read on these boards, pet insurance in the US (I know it's different elsewhere, esp. in the UK) isn't the greatest deal. I am hoping that as consumer demand grows, we will see an improvement in services.
I'm in the U.S., and it's been a fantastic deal for me. My insurer has paid out a lot for my cat's heart condition. This year he will hit his $2,500-per-condition cap, but I definitely got my money's worth. And I think the cat got diagnosed and treated more quickly, because I didn't factor the cost of tests into my decisions.