I'm split on this issue. On one hand I think that a corporation who finds it religiously offensive to provide contraceptives (which is a authentic reason, I think) should not be required to. Of course, the flip side is that it would be too easy for any company to claim they are a Christian company, saving money from not having to buy contraceptives.
I suppose there could be guidelines, but I still feel the system would be abused no matter what. Hobby Lobby, from my experience, would be a genuine case for this, but I suppose my final verdict would be to require everyone to comply regardless, as any sort of rules governing this could easily be avoided.