What he said. Ive done dozens of exhausts on cars before, but was shocked when I came to take the exhaust off my 4 year old, 20,000 mile zed. All the nuts / bolts were totally rusted like they were on some 100 year old barn find car. I couldnt believe it. Took me about 6 hours of messing about to get it off, including getting the angle grinder out and cutting the back box off in the end. Nightmare.
Others have said they have had no problems, so it might be okay for you.
Even after they chopped the bolts out, getting the backbox off the rubber mounts was a RIGHT biitch! Was under the car with my feet on the rear subframe for leverage, pulling the backbox towards me. Used a LOT of WD40 and in the end I nearly knocked myself out