HPCVC called for contributions to solve the requirements as set forth. There were five submissions, from Tesla, Electrify America, ABB, paXos, and Staubli. They were reviewed and graded based on how well they solved the requirements and on their technological readiness. The Task Force reviewed the submissions first online, and again after presentations at the in-person voting event on May 16. Ranked choice voting was used to select a winning submission. That winner has not yet been announced due to some further discussions taking place.
Source: https://assets.ctfassets.net/ucu418...HPCVCS_Task_Force_update_6.10.2019_Rustam.pdf
EPRI Public Site (see 04 - Bus and Truck Working Council June 2019 - CharIN HPCVCS Task Force update 6.10.2019 Rustam)
Tesla also is a member of the committee, so even if they don't use the Tesla proposal there's a good chance the Tesla semi will use whatever standard comes out.