Depends if what breaks was affected by the lift. If something with the engine, electronics, air conditioning, exhaust, etc is what is needing to be repaired, then the warranty will cover the repairs. If something related to the suspension or drive shaft breaks, it will not be covered because the lift could be viewed as what caused the failure.
My dealer told me as long as I get them to do the work they will warranty it. I bought the extended warranty and they told me their work will cover through the 7 years. I only have to use the lift kits and parts they offer and them do the work.