When a pipe freezes and cracks, very often the homeowner suffers water damage from the sudden and accidental discharge of water from the plumbing system. Most Homeowners Insurance policies cover this water damage to your home and its contents, subject to your deductible. Also, most Homeowners policies will cover the cost to get to the pipe. For example often the drywall has to be removed, and then also replaced after the pipe repair is taken care of. What is not covered is the actual repair of the pipe itself. This part of the plumbing repair is excluded and not a covered part of the loss.
The other common exclusion is for vacancy of the home if the homeowner leaves the home for an extended period of time, and does not take the necessary precautions to keep the home heated. If you turn off the heat and leave town for a few months there is no insurance coverage if a pipe freezes and cracks. As always check with your insurance company for the specific details on your policy in case it differs.