Sure there are routes that would be unsuited for EV right now, but it should be closer to 90/10 than 10/90.
Also I'm surprised by how –there's no other way to put this– stupid this program is. According to page 38 of the environmental impact statement[1], they're planning on using 94kWh battery packs for the EV version of these vans, giving an expected range of 70 miles. This makes no sense. Ford already makes an EV version of its Transit vans with 67kWh batteries and 100+ mile range. Moreover the environmental impact statement notes this on page 43! These vans can carry more cargo than the planned USPS vehicle and they can be bought for $47k retail today. Purchasing the vans would almost certainly be cheaper at such high volumes, saving billions of dollars compared to the Oshkosh contract.
Considering the amount of waste, my guess is that this program is a way to help out a defense contractor (Oshkosh).
1. https://uspsngdveis.com/documents/USPS%20NGDV%20Acquisitions...
The cost/time to bring up a production line for just these trucks doesn’t seem like it should be cheaper if their gas either. If anything, sharing a ‘skateboard’ with a delivery van or something would make it even easier.