Has anyone had epoxy lining done in their cast iron plumbing?

[Bruce P.]

So my friend is recently in a position where they may have to replace their main sewer line connecting the house to the street. One of the contractors said they had a new machine that could do epoxy lining of the cast iron plumbing system underneath the house. The upside is that they wouldn't have to dig up the floor or anything like that. The machine would apparently do the epoxy liner by being snaked thru the pipes is my understanding. 

Anyone know exactly if anything can go wrong with this and how costly that could be? Would my friend be better off getting new pipes if/when needed rather than doing an epoxy lining?