Hi Chaps
Many years ago it seemed to be a good way for a garage to make a few quid by saying your brake pipes are rusty, now I am reasonably sure most pipes these days a have a covering of some sort of protection either wax/underseal or coated with a thin coat of plastic. Look at the pipes from the master cylinder and you will see what I mean.
Brake pipes can and do corrode underneath if damaged by stones flicking up etc.
Some garages do tend to play on our fears for safety with brakes and I agree safety is paramount but my Omega is very old and MOTed at a Vauxhall dealer and never once has the tester if even advised a corroded brake pipe.
Some MOT testers seem to see a covering of wax with some dirt attached as corrosion. And if you clean it off you expose the metal to the elements.
I would say if you are having your pipes replaced, make sure you have it done with copper pipes or if using steel make sure you paint or underseal etc. or you will be doing it again 12 months time.
Regards
Mike