I wasn't aware that sharp curves were a dealbreaker for DPU; BNSF and UP use DPUs on Cajon Pass, which has some pretty dramatic curves, and I've seen NS DPUs on Horseshoe Curve.
Here's a video of a CSX DPU train on a sharp curve on the old L&N:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives