I have heard that when you buy a car, if you already own and insure another car, some insurance companies cover your newly bought car with the same coverage you have on your old car for a short period of time.
My friend found out the hard way that this works only with cars. If you own and insure a car, and you buy a bike, your company won't give you the grace period coverage on the bike. But, if you already insure a bike, and you buy another, the grace period coverage thing DOES apply.
I'm sure all companies aren't the same, but thats what his company told him when his bike was stolen 2 days after he bought it. My company told me the same thing when I asked them about it.