Unless the tubes are buckled, and the bend exceeds maybe 5 - 10 degrees and the brazing joints are not cracked or broken at the rear stays, I would think it has a good chance of still being cold set back into alignment. Especially if the frame tubes are not heat treated. I suspect that the misalignment is not that bad if it was riding OK before you got it to the shop, and should be fixable. It's possible that they just don't want to tackle the fix, because they have not cold set a frame before.....or just lazy to do so on an old, not so expensive bike.
Take it to a shop with good, competent mechanics and that deals with C&V bikes regularly to get a second opinion.