I believe the majority of them offer preventative care according to what I've read through previously, though I had opted not to go that route. I may very well in the future especially if I'm getting a pup young at least for its first year.
This is especially so if you're not just paying for the most basic plan they offer. They just don't generally cover pre-existing conditions so you'd want to get your dog insured before it ever *knocks on wood* gets diagnosed with any major problem but I hope that would never be the case for you.
Maybe check out the one Wylie's Mom is on? If I recall correctly, she's with Pet Plan and I know the vet just passed me a bunch of pamphlets during the last visit which included one from Pet Plan. This means we most definitely get that offered up here.
In the other pet insurance threads on this forum, I've seen people signed up with different companies... so it might just be the luck of the draw for which one is less anal in your specific area when it comes to sending you a compensation cheque for their end of the coverage. Good luck!