In some of the posts I've read on this site such as Is hacking legal when a friend allows you to attempt to hack their system?, and Best way to test my home network from the outside, users who responded pointed out that testers should notify or request permission from their ISP to do testing. I have difficulty imagining such requests would go over very well with an ISP. It seems they have everything to lose (from a liability point of view), and little to nothing to gain, from approving your request to perform penetration testing over their network.
Has anybody successfully asked an ISP for permission to do security related testing over their network? How would one do so?