If you do the copy thing that NIght suggested, you will of course still have to make amendments to delete assets purchased in 2016, 2017, 2018 and add assets the existed in 2015 but didn't in 2018. And your copy/paste method wouldn't pick up the correct Accum Depn through 2014 either. I'd rather not.
Since you have the 2015 tax return, just put in the 2015 total depn expense in the "override" field like beardenjv suggested. I had to do this recently, but then, without the detail on some of the forms, the amended AMT wouldn't calculate correctly, so I had to make a manual adjustment for that, too. Still easier than entering the 100 assets and all the other details the client had, tho.