What's old is new again.
Ford has had a series of Hydraulic Hybrid prototypes, the earliest I remember is this one from 2002:
2002 Ford F-350 Tonka Concept Images, Information and History | Conceptcarz.com
UPS has hydraulic hybrid delivery trucks that got ~50% better economy:
UPS to Roll Out Hydraulic Hybrids | Autopia | Wired.com