Its all hydrogen - not sure where you got natural gas from. I'm not sure who UPS is using. Most of these systems are a partnership with the chassis manufacturer and incorporate a big battery and the fuel cell is really a range extender that keeps the battery charged up - the smaller the battery the more you can say it is fuel cell powered though - even GenDrives have a LiIon battery
FedEx using PLUG in its trials using the same DoE grant (On the streets in California and soon Albany I believe)
USPS (the BIG one) is trialing a number of vehicles and suppliers (they have all sorts of requirements for their fleet) including one from Workhorse Technology (remember that name) which uses PLUG. They already use PLUG GenDrives in a sorting facility in MD/DC
Amazon is of course working with PLUG for its new delivery fleet including automated "robots" to deliver in cities along the street (think R2D2) and working with Workhorse on the Delivery vehicle with Drone all powered by Fuel cells.
Then we have one of the "big three" automotive groups in China with Furui about to embark on road trials following certification of the ProGen Engines.